Redox polymerizable composition with photolabile transition metal complexes

ABSTRACT

Polymerizable compositions comprising a redox initiator system is disclosed. The redox initiator system comprises a photolabile transition metal complex that photolyzes and initiates the redox cycle. Dental compositions comprising dental resins and the photolabile redox initiator system are also described.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. 371 ofPCT/US2016/055619, filed Oct. 6, 2016, which claims the benefit of U.S.Application No. 62/251,931, filed Nov. 6, 2015, the disclosure of whichis incorporated by reference in its/their entirety herein.

BACKGROUND

Redox reactions represent an important method for initiating the curingof acrylate, methacrylate and other vinyl-based resin, includingadhesive and dental formulations. Redox-initiated curing often hasadvantages over photoinitiated curing, including improved depth of cureand a slower accumulation of stress during the initial stages of curing.

A significant challenge in the use of redox initiating systems isfinding an optimal balance between stability and reactivity. Thereactivity of the redox system needs to be sufficiently high to achievefull curing and obtain the desired physical properties within a shortperiod of time. However, if the reactivity is too great, problems suchas premature curing, accumulation of stress, and poor shelf stability ofthe formulation can be encountered.

SUMMARY

The present disclosure provides a method to overcome these problems bycreating an “on demand” redox-initiated cure, in which the transitionmetal complex of the redox cure initiator system has latent activitywhile the formulation is stored and delivered, but then can be triggeredwhen required.

The present disclosure provides a redox initiator system for initiatingpolymerization comprising an oxidizing agent, a reducing agent, andphotolabile transition metal complex that participates in a redox cycle.On exposure to actinic radiation, such as UV, the transition metalcomplex photolyzes, releasing the transition metal and initiating theredox-initiated polymerization. Advantageously, polymerization of theinstant compositions may be initiated by exposure to actinic radiation,but continued irradiation is not required. When the redox initiatorsystem is combined with polymerizable monomers to form a polymerizablecomposition, the polymerization may be initiated, then the compositionbuilds molecular weight and physical properties as the compositioncontinues to cure in the absence of light.

In one aspect, this disclosure provides a polymerizable compositioncomprising one or more ethylenically-unsaturated polymerizable monomersor oligomers and an initiator system that participates in a redox cycle.

In another aspect, this disclosure provides a polymerizable dentalcomposition comprising a polymerizable dental resin and the initiatorsystem that participates in a redox cycle.

DETAILED DESCRIPTION

The chemically polymerizable compositions comprise a polymerizablecomponent (an ethylenically unsaturated polymerizable component,including monomers and oligomers) and a redox initiator system thatincludes the photolabile transition metal complex, an oxidizing agent,and a reducing agent.

The photolabile transition metal complex is of the general formula:

whereinR^(Photo) is a photolabile group;M⁺ is a transition metal that participates in a redox cycle;each X¹ and X² is independently selected from —N—, —S—, and —O—;each X³ and X⁴ is independently selected from the group consisting of—NR¹—, and —S—;each R¹ is independently selected from the group consisting of: H,alkyl, cycloalkyl, heterocycloalkyl, arylalkyl, heteroarylalkyl, alkoxy,halo, formyl, hydroxyl, acyl, aryloxy, alkylthio, amino, alkylamino,arylalkylamino, disubstituted amino, acylamino, acyloxy, ester, amide,and carboxyalkyl;each adjacent pair of R¹ and R² can independently form aheterocycloalkyl or heteroaryl group with respective heteroatom X³ orX⁴;each of R², R³, R⁴, R⁵, R⁶, and R⁷ is independently selected from thegroup consisting of: H, alkyl, alkenyl, alkynyl, cycloalkyl,cycloalkylalkyl, cycloalkylalkenyl, cycloalkylalkynyl, heterocyclo,heterocycloalkyl, heterocycloalkenyl, heterocycloalkynyl, aryl,arylalkyl, arylalkenyl, arylalkynyl, heteroaryl, heteroarylalkyl,heteroarylalkenyl, heteroarylalkynyl, alkoxy, halo, mercapto, azido,cyano, formyl, carboxylic acid, carboxyalkyl, hydroxyl, nitro, acyl,aryloxy, alkylthio, amino, alkylamino, arylalkylamino, disubstitutedamino, acylamino, acyloxy, ester, amide, sulfoxyl, sulfonyl, sulfonate,sulfonic acid, sulfonamide, urea, alkoxylacylamino, and aminoacyloxy;with the proviso that R³ is absent when R¹ and R² form a heteroarylgroup with respective heteroatom X³ or X⁴;R⁴ and R⁵ can together form oxo; or R⁶ and R⁷ can together form oxo;x is from 1 to 2; and y is from 1 to 3; or a salt thereof.

In some preferred embodiments, the photolabile transition metal complexis of the formula:

Wherein

R^(Photo) is a photolabile group;

M⁺ is a transition metal that participates in a redox cycle;

each X¹ and X² is independently selected from —N—, —S—, and —O—;

each X³ and X⁴ is independently selected from the group consisting of—NR¹—, and —S—;

each R¹ is independently selected from the group consisting of: H,alkyl, cycloalkylalkyl, heterocycloalkyl, arylalkyl, heteroarylalkyl,alkoxy, halo, formyl, hydroxyl, acyl, aryloxy, alkylthio, amino,alkylamino, arylalkylamino, disubstituted amino, acylamino, acyloxy,ester, amide, and carboxyalkyl;each of R², R³, R⁴, R⁵, R⁶, and R⁷ is independently selected from thegroup consisting of:

-   -   H, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl,        cycloalkylalkenyl, cycloalkylalkynyl, heterocyclo,        heterocycloalkyl, heterocycloalkenyl, heterocycloalkynyl, aryl,        arylalkyl, arylalkenyl, arylalkynyl, heteroaryl,        heteroarylalkyl, heteroarylalkenyl, heteroarylalkynyl, alkoxy,        halo, mercapto, azido, cyano, formyl, carboxylic acid,        carboxyalkyl, hydroxyl, nitro, acyl, aryloxy, alkylthio, amino,        alkylamino, arylalkylamino, disubstituted amino, acylamino,        acyloxy, ester, amide, sulfoxyl, sulfonyl, sulfonate, sulfonic        acid, sulfonamide, urea, alkoxylacylamino, and aminoacyloxy;        R⁴ and R⁵ can together form oxo; or R⁶ and R⁷ can together form        oxo;        R⁸ and R⁹ are independently a hydrocarbyl group when taken with        X³ and X⁴ respectively for a heterocyclic group or a        heteroaromatic group, with the proviso that R³ is absent when R¹        and R² form a heteroaryl group with respective heteroatom X³— or        X⁴;        x is from 1 to 2; and y is from 1 to 3; or a salt thereof.

Any known photolabile group that may be irradiated and which cleaves orfragments to release the transition metal may be used. Reference may bemade to Petr Klan et al., Photoremovable Protecting Groups in Chemistryand Biology: Reaction Mechanisms and Efficiency, Chem. Reviews, 2013,vol. 113, pp 119-191 and Jacob Wirz et al., Photoremovable ProtectingGroups: Reaction Mechanisms and Applications, Photochem. Photobiol.Sci., 2002, Vol. 1, pp. 441-458.

With reference to Formulas I and II, useful photolabile groups“R^(Photo)” include, but are not limited to, phenacyl groups,2-alkylphenacyl groups, ethylene-bridged phenacyl groups,p-hydroxyphenacyl groups, benzoin groups, o-nitrobenzyl groups,o-nitro-2-phenethylloxycarbonyl groups, coumarin-4-yl methyl groups,benzyl groups, o-hydroxylbenzyl groups, o-hydroxynapthyl groups,2,5-dihydroxyl benzyl groups, 9-phenylthioxanthyl, 9-phenylxanthylgroups, anthraquinon-2-yl groups, 8-halo-7-hydroxyquinoline2-yl methylgroups, pivaloylglycol groups.

In some preferred embodiments, the transition metal complex may berepresented by Formula III:

where R^(Photo) is a photolabile group;M⁺ is a transition metal that participates in a redox cycle;the bracketed carbonyl oxygen may be present or absent, and if absent isdefined for R⁴ and R⁵ supra, and are preferably H; andR^(hetero) is selected from pyridine, imidazole and thiophene rings.

Useful photolabile groups include the following. It will be understoodthat the pyridine groups are illustrated for simplicity for the—R¹—R²—X³— or —R¹—R²—X⁴— or group of Formula I, or the —R⁸—X³— or theR⁹—X⁴— groups of Formula II, and are not intended to limit the scope orinterpretation of the compounds of Formulas I or II. Further, thearomatic groups, particularly the phenyl groups, may be furthersubstituted by alkyl, aryl, halide, or hydroxy groups. The transitionmetal, shown as M⁺, is also not shown for simplicity. The illustratedphenyl groups may further be substituted for napthyl, biphenyl,phenanthrenyl or anthracenyl groups. The mode of photocleavage isillustrated by the ˜.

Useful transition metals, M⁺, include the catalytically active valencestates of Cu, Fe, Ru, Cr, Mo, Pd, Ni, Pt, Mn, Rh, Re, Co, V, Au, Nb andAg. Preferred low valent metals include Cu(II), Fe(II), Co(II), Pt(II)and Ru(II). Other valent states of these same metals may be used, andthe catalytically active valence states generated in situ.

The compounds of Formulas I-III may be prepared as described in U.S.Pat. No. 8,440,827 (Franz et al.), incorporated herein by reference.

The molar proportion of photolabile transition metal complex (ofFormulas I-III) relative to oxidizing agent (or reducing agent) isgenerally that which is effective to polymerize the selectedpolymerizable component(s), but may be from 1:1000 to 1:5, preferablyfrom 1:500 to 1:25, more preferably from 1:250 to 1:50, and mostpreferably from 1:200 to 1:75. The oxidant and reductant of the redoxinitiator system are used in approximately equimolar amount. Generallythe mole ratio of the oxidant and reductant is from 1:1.5 to 1.5:1,preferably 1:1.1 to 1.1 to 1.

Useful reducing agents include ascorbic acid, ascorbic acid derivatives,and metal complexed ascorbic acid compounds as described in U.S. Pat.No. 5,501,727 (Wang et al.); amines, especially tertiary amines, such as4-tert-butyl dimethylaniline; aromatic sulfinic salts, such asp-toluenesulfinic salts and benzenesulfinic salts; thioureas, such as1-ethyl-2-thiourea, tetraethyl thiourea, tetramethyl thiourea,1,1-dibutyl thiourea, and 1,3-dibutyl thiourea; barbituric acid and1-benzyl-5-phenyl barbituric acid; beta-diketones, including dimedone,2-methylcyclohexane-1,3-dione, 2-methylcyclopentane-1,3-dione, and3-methyl-2,4-pentanedione; beta-diesters, including2,2-dimethyl-1,3-dioxane-4,6-dione,2,2,5-trimethyl-1,3-dioxane-4,6-dione,2,2-dimethyl-5-phenyl-1,3-dioxane-4,6-dione, and dimethyl malonate, andmixtures thereof. Other secondary reducing agents may include cobalt(II) chloride, ferrous chloride, ferrous sulfate, hydrazine,hydroxylamine (depending on the choice of oxidizing agent), salts of adithionite or sulfite anion, and mixtures thereof. Preferably, thereducing agent is an ascorbic acid derivative.

Suitable oxidizing agents will also be familiar to those skilled in theart, and include but are not limited to persulfuric acid and saltsthereof, such as sodium, potassium, ammonium, cesium, and alkyl ammoniumsalts. Preferable oxidizing agents include peroxides such as benzoylperoxides, hydroperoxides such as cumyl hydroperoxide, t-butylhydroperoxide, and amyl hydroperoxide, as well as salts of transitionmetals such as cobalt (III) chloride and ferric chloride, cerium (IV)sulfate, perboric acid and salts thereof, permanganic acid and saltsthereof, perphosphoric acid and salts thereof, and mixtures thereof.

The reducing and oxidizing agents are present in amounts sufficient topermit an adequate free radical reaction rate. This can be evaluated bycombining all of the ingredients of the polymerizable composition exceptfor the optional filler, and observing whether or not a hardened mass isobtained.

Preferably, the reducing agent is present in an amount of at least 0.01%by weight, and more preferably at least 0.1% by weight, based on thetotal weight of the polymerizable components of the polymerizablecomposition. Preferably, the reducing agent is present in an amount ofno greater than 10% by weight, and more preferably no greater than 5% byweight, based on the total weight (including water) of the polymerizablecomponents of the polymerizable composition.

Preferably, the oxidizing agent is present in an amount of at least0.01% by weight, and more preferably at least 0.10% by weight, based onthe total weight of the polymerizable components of the polymerizablecomposition. Preferably, the oxidizing agent is present in an amount ofno greater than 10% by weight, and more preferably no greater than 5% byweight, based on the total weight of the polymerizable components of thepolymerizable composition.

In general, the oxidizing agent and reducing agent are chosen so theyare not directly reactive, and require the presence of the transitionmetal to effect the redox cycle, as is known in the art. The componentsof the polymerizable composition may be segregated to prevent prematurereactions. In particular it is desirable to segregate the transitionmetal complex and the reducing agent, prior to reaction. In particular,it is beneficial to have a “two-part” system in which the polymerizablemonomers, the oxidizing agent and the transition metal complex is in thefirst mixture, and the reducing agent and any filler or other additivesare in a second mixture.

The present disclosure further provides a polymerizable compositioncomprising the redox initiator system (including labile transition metalcomplex, oxidant and reductant), and at least one polymerizable monomer,such as vinyl monomers, and (meth)acryloyl monomers (including acrylateesters, amides, and acids to produce (meth)acrylate homo- andcopolymers). The redox initiator system is present in the composition inamounts, from about 0.1 to about 10 parts by weight, preferably 0.1 to 5parts by weight, based on 100 parts by weight of the polymerizablecomponent of the polymerizable composition.

In some embodiments, the polymerizable composition comprises the redoxinitiator system and one or more vinyl monomers. Vinyl monomers usefulin the polymerizable composition include vinyl ethers (e.g. methyl vinylether, ethyl vinyl ether), vinyl esters (e.g., vinyl acetate and vinylpropionate), styrene, substituted styrene (e.g., α-methyl styrene),vinyl halide, divinylbenzene, alkenes (e.g. propylene, isomers ofbutylene, pentene, hexene up to dodecene, isoprene, butadiene) andmixtures thereof.

In some embodiments the polymerizable composition comprises one or more(meth)acrylate ester monomer(s). (Meth)acrylate ester monomer useful inpreparing (meth)acrylate (co)polymers are monomeric (meth)acrylic esterof a non-tertiary alcohol, which alcohol contains from 1 to 14 carbonatoms and preferably an average of from 4 to 12 carbon atoms.

Examples of monomers suitable for use as the (meth)acrylate estermonomer include the esters of either acrylic acid or methacrylic acidwith non-tertiary alcohols such as ethanol, 1-propanol, 2-propanol,1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol,2-methyl-1-butanol, 3-methyl-1-butanol, 1-hexanol, 2-hexanol,2-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol,3,5,5-trimethyl-1-hexanol, 3-heptanol, 1-octanol, 2-octanol,isooctylalcohol, 2-ethyl-1-hexanol, 1-decanol, 2-propylheptanol,1-dodecanol, 1-tridecanol, 1-tetradecanol, citronellol,dihydrocitronellol, and the like. In some embodiments, the preferred(meth)acrylate ester monomer is the ester of (meth)acrylic acid withbutyl alcohol or isooctyl alcohol, or a combination thereof, althoughcombinations of two or more different (meth)acrylate ester monomer aresuitable. In some embodiments, the preferred (meth)acrylate estermonomer is the ester of (meth)acrylic acid with an alcohol derived froma renewable source, such as 2-octanol, citronellol, ordihydrocitronellol.

In some embodiments it is desirable for the (meth)acrylic acid estermonomer to include a high T_(g) monomer. The homopolymers of these highT_(g) monomers have a T_(g) of at least 25° C., and preferably at least50° C. Examples of suitable monomers useful in the present inventioninclude, but are not limited to, t-butyl acrylate, methyl methacrylate,ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate,isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate,stearyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate,isobornyl acrylate, isobornyl methacrylate, benzyl methacrylate, 3,3,5trimethylcyclohexyl acrylate, cyclohexyl acrylate, N-octyl acrylamide,and propyl methacrylate or combinations.

The (meth)acrylate ester monomer is present in an amount of up to 100parts by weight, preferably 85 to 99.5 parts by weight based on 100parts total monomer content used to prepare the polymer, exclusive ofthe amount of multifunctional (meth)acrylates. Preferably (meth)acrylateester monomer is present in an amount of 90 to 95 parts by weight basedon 100 parts total monomer content. When high T_(g) monomers areincluded, the copolymer may include up to 50 parts by weight, preferablyup to 20 parts by weight of the (meth)acrylate ester monomer component.

The polymerizable composition may comprise an acid functional monomer,where the acid functional group may be an acid per se, such as acarboxylic acid, or a portion may be a salt thereof, such as an alkalimetal carboxylate. Useful acid functional monomers include, but are notlimited to, those selected from ethylenically unsaturated carboxylicacids, ethylenically unsaturated sulfonic acids, ethylenicallyunsaturated phosphonic or phosphoric acids, and mixtures thereof.Examples of such compounds include those selected from acrylic acid,methacrylic acid, itaconic acid, fumaric acid, crotonic acid, citraconicacid, maleic acid, oleic acid, β-carboxyethyl (meth)acrylate,2-sulfoethyl methacrylate, styrene sulfonic acid,2-acrylamido-2-methylpropanesulfonic acid, vinylphosphonic acid, andmixtures thereof.

Due to their availability, acid functional monomers of the acidfunctional copolymer are generally selected from ethylenicallyunsaturated carboxylic acids, i.e. (meth)acrylic acids. When evenstronger acids are desired, acidic monomers include the ethylenicallyunsaturated sulfonic acids and ethylenically unsaturated phosphonicacids. The acid functional monomer is generally used in amounts of 0.5to 15 parts by weight, preferably 1 to 15 parts by weight, mostpreferably 5 to 10 parts by weight, based on 100 parts by weight totalmonomer.

The polymerizable composition may comprise a polar monomer. The polarmonomers useful in preparing the copolymer are both somewhat oil solubleand water soluble, resulting in a distribution of the polar monomerbetween the aqueous and oil phases in an emulsion polymerization. Asused herein the term “polar monomers” are exclusive of acid functionalmonomers.

Representative examples of suitable polar monomers include but are notlimited to 2-hydroxyethyl (meth)acrylate; N-vinylpyrrolidone;N-vinylcaprolactam; acrylamide; mono- or di-N-alkyl substitutedacrylamide; t-butyl acrylamide; dimethylaminoethyl acrylamide; N-octylacrylamide; tetrahydrofurfuryl (meth)acrylate, poly(alkoxyalkyl)(meth)acrylates including 2-(2-ethoxyethoxy)ethyl (meth)acrylate,2-ethoxyethyl (meth)acrylate, 2-methoxyethoxyethyl (meth)acrylate,2-methoxyethyl methacrylate, polyethylene glycol mono(meth)acrylates;alkyl vinyl ethers, including vinyl methyl ether; and mixtures thereof.Preferred polar monomers include those selected from the groupconsisting of tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl(meth)acrylate and N-vinylpyrrolidinone. The polar monomer may bepresent in amounts of 0 to 10 parts by weight, preferably 0.5 to 5 partsby weight, based on 100 parts by weight total monomer.

The polymerizable composition may further comprise a vinyl monomer whenpreparing acrylic copolymers. When used, vinyl monomers useful in the(meth)acrylate polymer include vinyl esters (e.g., vinyl acetate andvinyl propionate), styrene, substituted styrene (e.g., α-methylstyrene), vinyl halide, divinylbenzene, and mixtures thereof. As usedherein vinyl monomers are exclusive of acid functional monomers,acrylate ester monomers and polar monomers. Such vinyl monomers aregenerally used at 0 to 5 parts by weight, preferably 1 to 5 parts byweight, based on 100 parts by weight total monomer when preparingacrylic copolymers.

A multifunctional (meth)acrylate may be incorporated into the blend ofpolymerizable monomers. Examples of useful multifunctional(meth)acrylates include, but are not limited to, di(meth)acrylates,tri(meth)acrylates, and tetra(meth)acrylates, such as 1,6-hexanedioldi(meth)acrylate, poly(ethylene glycol) di(meth)acrylates, polybutadienedi(meth)acrylate, polyurethane di(meth)acrylates, and propoxylatedglycerin tri(meth)acrylate, and mixtures thereof. The amount andidentity of multifunctional (meth)acrylate is tailored depending uponapplication of the adhesive composition, for example, adhesives,hardcoats or dental resins.

Typically, the multifunctional (meth)acrylate is present in amounts upto 100 parts, preferably 0.1 to 100 parts, based 100 parts by weight ofremaining polymerizable monofunctional monomers. In some embodiments themultifunctional (meth)acrylate is used in amounts of greater than 50parts by weight, based on the 100 parts by weight of remainingpolymerizable monomers. In some embodiments, the multifunctional(meth)acrylate may be present in amounts from 0.01 to 5 parts,preferably 0.05 to 1 parts, based on 100 parts total monomers of thepolymerizable composition for adhesive applications, and greater amountsfor hardcoats or dental resins, as described herein.

In such embodiments, an acrylic copolymer may be prepared from apolymerizable composition comprising:

-   -   i. up to 100 parts by weight, preferably 85 to 99.5 parts by        weight of an (meth)acrylic acid ester;    -   ii. 0 to 15 parts by weight, preferably 0.5 to 15 parts by        weight of an acid functional ethylenically unsaturated monomer;    -   iii. 0 to 15 parts by weight of a non-acid functional,        ethylenically unsaturated polar monomer;    -   iv. 0 to 5 parts by weight vinyl monomer;    -   v. 0 to 100 parts by weight of a multifunctional (meth)acrylate,        preferably 50 to 100 parts by weight, relative to i-iv;        and    -   vi. the redox initiator system (including the photolabile        complex, oxidant and reductant) in amounts from about 0.1 weight        percent to about 5.0 weight percent, relative to 100 parts total        monomer i-v.

The curable composition may also include other additives. Examples ofsuitable additives include tackifiers (e.g., rosin esters, terpenes,phenols, and aliphatic, aromatic, or mixtures of aliphatic and aromaticsynthetic hydrocarbon resins), surfactants, plasticizers (other thanphysical blowing agents), nucleating agents (e.g., talc, silica, orTiO₂), pigments, dyes, reinforcing agents, solid fillers, stabilizers(e.g., UV stabilizers), and combinations thereof. The additives may beadded in amounts sufficient to obtain the desired properties for thecured composition being produced. The desired properties are largelydictated by the intended application of the resultant polymeric article.

Adjuvants may optionally be added to the compositions such as colorants,abrasive granules, anti-oxidant stabilizers, thermal degradationstabilizers, light stabilizers, conductive particles, tackifiers, flowagents, bodying agents, flatting agents, inert fillers, binders, blowingagents, fungicides, bactericides, surfactants, plasticizers, rubbertougheners and other additives known to those skilled in the art. Theyalso can be substantially unreactive, such as fillers, both inorganicand organic. These adjuvants, if present, are added in an amounteffective for their intended purpose.

In some embodiments, a toughening agent may be used. The tougheningagents which are useful in the present invention are polymeric compoundshaving both a rubbery phase and a thermoplastic phase such as: graftpolymers having a polymerized, diene, rubbery core and a polyacrylate,polymethacrylate shell; graft polymers having a rubbery, polyacrylatecore with a polyacrylate or polymethacrylate shell; and elastomericparticles polymerized in situ in the epoxide from free radicalpolymerizable monomers and a copolymerizable polymeric stabilizer.

Examples of useful toughening agents of the first type include graftcopolymers having a polymerized, diene, rubbery backbone or core towhich is grafted a shell of an acrylic acid ester or methacrylic acidester, monovinyl aromatic hydrocarbon, or a mixture thereof, such asdisclosed in U.S. Pat. No. 3,496,250 (Czerwinski), incorporated hereinby reference. Preferable rubbery backbones comprise polymerizedbutadiene or a polymerized mixture of butadiene and styrene. Preferableshells comprising polymerized methacrylic acid esters are lower alkyl(C₁-C₄) substituted methacrylates. Preferable monovinyl aromatichydrocarbons are styrene, alphamethylstyrene, vinyltoluene, vinylxylene,ethylvinylbenzene, isopropylstyrene, chlorostyrene, dichlorostyrene, andethylchlorostyrene. It is important that the graft copolymer contain nofunctional groups that would poison the catalyst.

Examples of useful toughening agents of the second type are acrylatecore-shell graft copolymers wherein the core or backbone is apolyacrylate polymer having a glass transition temperature below about0° C., such as polybutyl acrylate or polyisooctyl acrylate to which isgrafted a polymethacrylate polymer (shell) having a glass transitionabove about 25° C., such as polymethylmethacrylate.

The third class of toughening agents useful in the invention compriseselastomeric particles that have a glass transition temperature (T_(g))below about 25° C. before mixing with the other components of thecomposition. These elastomeric particles are polymerized from freeradical polymerizable monomers and a copolymerizable polymericstabilizer that is soluble in the resins. The free radical polymerizablemonomers are ethylenically unsaturated monomers or diisocyanatescombined with coreactive difunctional hydrogen compounds such as diols,diamines, and alkanolamines.

Useful toughening agents include core/shell polymers such asmethacrylate-butadiene-styrene (MBS) copolymer wherein the core iscrosslinked styrene/butadiene rubber and the shell is polymethylacrylate(for example, ACRYLOID KM653 and KM680, available from Rohm and Haas,Philadelphia, Pa.), those having a core comprising polybutadiene and ashell comprising poly(methyl methacrylate) (for example, KANE ACE M511,M521, B11A, B22, B31, and M901 available from Kaneka Corporation,Houston, Tex. and CLEARSTRENGTH C223 available from ATOFINA,Philadelphia, Pa.), those having a polysiloxane core and a polyacrylateshell (for example, CLEARSTRENGTH S-2001 available from ATOFINA andGENIOPERL P22 available from Wacker-Chemie GmbH, Wacker Silicones,Munich, Germany), those having a polyacrylate core and a poly(methylmethacrylate) shell (for example, PARALOID EXL2330 available from Rohmand Haas and STAPHYLOID AC3355 and AC3395 available from Takeda ChemicalCompany, Osaka, Japan), those having an MBS core and a poly(methylmethacrylate) shell (for example, PARALOID EXL2691A, EXL2691, andEXL2655 available from Rohm and Haas) and the like and mixtures thereof.Preferred modifiers include the above-listed ACRYLOID and PARALOIDmodifiers and the like, and mixtures thereof.

The toughening agent is useful in an amount equal to about 1-35 parts byweight, preferably about 3-25 parts by weight, relative to 100 parts byweight of the polymerizable component of the polymerizable composition.The toughening agent adds strength to the composition after curingwithout reacting with the component of the curable composition orinterfering with curing.

In some embodiments the crosslinkable composition may include filler. Insome embodiments the total amount of filler is at most 50 wt. %,preferably at most 30 wt. %, and more preferably at most 10 wt. %filler. Fillers may be selected from one or more of a wide variety ofmaterials, as known in the art, and include organic and inorganicfiller. Inorganic filler particles include silica, submicron silica,zirconia, submicron zirconia, and non-vitreous microparticles of thetype described in U.S. Pat. No. 4,503,169 (Randklev).

Filler components include nanosized silica particles, nanosized metaloxide particles, and combinations thereof. Nanofillers are alsodescribed in U.S. Pat. No. 7,090,721 (Craig et al.), U.S. Pat. No.7,090,722 (Budd et al.), U.S. Pat. No. 7,156,911 (Kangas et al.), andU.S. Pat. No. 7,649,029 (Kolb et al.).

In some embodiments the filler may be surface modified. A variety ofconventional methods are available for modifying the surface ofnanoparticles including, e.g., adding a surface-modifying agent tonanoparticles (e.g., in the form of a powder or a colloidal dispersion)and allowing the surface-modifying agent to react with thenanoparticles. Other useful surface-modification processes are describedin, e.g., U.S. Pat. No. 2,801,185 (Iler), U.S. Pat. No. 4,522,958 (Daset al.) U.S. Pat. No. 6,586,483 (Kolb et al.), each incorporated hereinby reference.

Surface-modifying groups may be derived from surface-modifying agents.Schematically, surface-modifying agents can be represented by theformula X-Y, where the X group is capable of attaching to the surface ofthe particle (i.e., the silanol groups of a silica particle) and the Ygroup is a reactive or non-reactive functional group. A non-functionalgroup does not react with other components in the system (e.g. thesubstrate). Non-reactive functional groups can be selected to render theparticle relatively more polar, relatively less polar or relativelynon-polar. In some embodiments the non-reactive functional group “Y” isa hydrophilic group such as an acid group (including carboxylate,sulfonate and phosphonate groups), ammonium group or poly(oxyethylene)group, or hydroxyl group. In other embodiments, “Y” may be a reactivefunctional groups such as an ethylenically unsaturated polymerizablegroup, including vinyl, allyl, vinyloxy, allyloxy, and (meth)acryloyl,that may be free-radically polymerized with the polymerizable resin ormonomers.

Such optional surface-modifying agents may be used in amounts such that0 to 100%, generally 1 to 90% (if present) of the surface functionalgroups (Si—OH groups) of the silica nanoparticles are functionalized.The number of functional groups is experimentally determined wherequantities of nanoparticles are reacted with an excess of surfacemodifying agent so that all available reactive sites are functionalizedwith a surface modifying agent. Lower percentages of functionalizationmay then be calculated from the result. Generally, the amount of surfacemodifying agent is used in amount sufficient to provide up to twice theequal weight of surface modifying agent relative to the weight ofinorganic nanoparticles. When used, the weight ratio of surfacemodifying agent to inorganic nanoparticles is preferably 2:1 to 1:10. Ifsurface-modified silica nanoparticles are desired, it is preferred tomodify the nanoparticles prior to incorporation into the coatingcomposition.

The present polymerizable compositions are also useful in thepreparation of hardcoats and structural or semi-structural adhesives.The term “hardcoat” or “hardcoat layer” means a layer or coating that islocated on the external surface of an object, where the layer or coatinghas been designed to at least protect the object from abrasion.

The present disclosure provides hardcoat compositions comprising theredox initiator system of Formulas I and II and, a multi-functional(meth)acrylate monomer comprising two (preferably three) or more(meth)acrylate groups, and/or a multi-functional (meth)acrylate oligomerand optionally a (meth)acrylate-functional diluent.

In some embodiments, the polymerizable composition provides a structuraland/or semi-structural adhesive composition in which the partially curedcomposition may be disposed between two substrates (or adherends), andsubsequently fully cured to effect a structural or semi-structural bondbetween the substrates. “Semi-structural adhesives” are those curedadhesives that have an overlap shear strength of at least about 0.5 MPa,more preferably at least about 1.0 MPa, and most preferably at leastabout 1.5 MPa. Those cured adhesives having particularly high overlapshear strength, however, are referred to as structural adhesives.“Structural adhesives” are those cured adhesives that have an overlapshear strength of at least about 3.5 MPa, more preferably at least about5 MPa, and most preferably at least about 7 MPa.

Useful multifunctional (meth)acrylate monomers comprise three or more(meth)acrylate groups. Multifunctional (meth)acrylate monomers areuseful in the practice of the present invention because they addabrasion resistance to the hard coat layer. Preferred multifunctional(meth)acrylate monomers comprising three or more (meth)acrylate groupsinclude trimethylol propane tri(meth)acrylate (TMPTA), pentaerythritoltri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentrithritoltri(meth)acrylate (Sartomer 355), dipentaerythritol penta(meth)acrylate(Sartomer 399), dipentaerythritol hydroxy penta(meth)acrylate (DPHPA),glyceryl propoxy tri(meth)acrylate, trimethylopropane tri(meth)acrylate,and mixtures thereof Another useful radiation-curable component of thepresent invention is the class of multifunctional (meth)acrylateoligomers, having two or more (meth)acrylate groups, and having anaverage molecular weight (Mw) in the range from about 400 to 2000.

Useful multifunctional (meth)acrylate oligomers include polyester(meth)acrylates, polyurethane (meth)acrylates, and (meth)acrylated epoxy(meth)acrylates. (Meth)acrylated epoxy (meth)acrylates andpolyester(meth)acrylates are most preferred because they tend to have arelatively low viscosity and therefore allow a more uniform layer to beapplied by the spin coating method. Specifically, preferredmultifunctional (meth)acrylate oligomers include those commerciallyavailable from UCB Radcure, Inc. of Smyrna, Ga. and sold under the tradename Ebecryl (Eb): Eb40 (tetrafunctional acrylated polyester oligomer),ENO (polyester tetra-functional (meth)acrylate oligomer), Eb81(multifunctional (meth)acrylated polyester oligomer), Eb600 (bisphenol Aepoxy di(meth)acrylate), Eb605 (bisphenol A epoxy di(meth)acrylatediluted with 25% tripropylene glycol di(meth)acrylate), Eb639 (novolacpolyester oligomer), Eb2047 (trifunctional acrylated polyesteroligomer), Eb3500 (di-functional Bisphenol-A oligomer acrylate), Eb3604(multi-functional polyester oligomer acrylate), Eb6602 (trifunctionalaromatic urethane acrylate oligomer), Eb8301 (hexafunctional aliphaticurethane acrylate), EbW2 (difunctional aliphatic urethane acrylateoligomer), and mixtures thereof. Of these, the most preferred are, Eb600, Eb605, Eb80, and Eb81.

In some embodiments, the multifunctional (meth)acrylate oligomers maycomprise a reactive oligomer having pendent polymerizable groupscomprising:

a) greater than 50 parts by weight, preferably greater than 75 parts byweight, most preferably greater than 80 parts by weight of(meth)acrylate ester monomer units;

b) 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, mostpreferably 1 to 3 parts by weight, of monomer units having a pendent,free-radically polymerizable functional groups,

c) 0 to 20 parts by weight of other polar monomer units, wherein the sumof the monomer units is 100 parts by weight.

The reactive oligomer may be redox polymerized per se, or with amultifunctional acrylate, such as hexanediol di(meth)acrylate. Themonomer component may further comprise a diluent monomer, as described.The reactive oligomer having pendent polymerizable groups may beprepared as described in U.S. Pat. No. 7,598,298 (Lewandowski et al.),U.S. Pat. No. 7,342,047 (Lewandowski et al.) and U.S. Pat. No. 7,074,839(Fansler et al.), each incorporated herein by reference.

The (meth)acrylate-functional diluents, also referred to herein as“reactive diluents”, are relatively low molecular weight mono- ordi-functional, non-aromatic, (meth)acrylate monomers. These relativelylow molecular weight reactive diluents are advantageously of arelatively low viscosity, e.g., less than about 30 centipoise (cps) at25° C. Di-functional, non-aromatic (meth)acrylates are generallypreferred over mono-functional non-aromatic (meth)acrylates becausedi-functional non-aromatic (meth)acrylates allow for quicker cure time.Preferred reactive diluents include 1,6-hexanediol di(meth)acrylate(HDDA from UCB Radcure, Inc. of Smyrna, Ga.), tripropylene glycoldi(meth)acrylate, isobornyl (meth)acrylate (1130A, Radcure),2(2-ethoxyethoxy) ethyl (meth)acrylate (sold under the trade nameSartomer 256 from SARTOMER Company, Inc. of Exton, Pa.), n-vinylformamide (Sartomer 497), tetrahydrofurfuryl (meth)acrylate(Sartomer285), polyethylene glycol di(meth)acrylate (Sartomer 344), tripropyleneglycol di(meth)acrylate (Radcure), neopentyl glycol dialkoxydi(meth)acrylate, polyethyleneglycol di(meth)acrylate, and mixturesthereof.

In some embodiments the polymerizable composition may comprise:

20-80 wt. % of multifunctional (meth)acrylate monomers and/ormultifunctional (meth)acrylate oligomers,

0 to 25 wt. % range of (meth)acrylate diluent, (0-25 wt. %);

20 to 75 wt. % of silica (per se, whether or not functionalized), and

from about 0.1 weight percent to about 5.0 weight percent of the redoxinitiator, based on the total weight of the polymerizable composition.

In some embodiments the amount of silica, including the silica modifiedwith conventional surface modifying agents and unmodified silica is20-75 wt. %., preferably 50-70 wt. %.

Filler components include nanosized silica particles, nanosized metaloxide particles, and combinations thereof. Nanofillers are alsodescribed in U.S. Pat. No. 7,090,721 (Craig et al.), U.S. Pat. No.7,090,722 (Budd et al.), U.S. Pat. No. 7,156,911 (Kangas et al.), andU.S. Pat. No. 7,649,029 (Kolb et al.).

The present polymerization may be conducted in bulk, or in a solvent.Solvents, preferably organic, can be used to assist in the dissolutionof the initiator and initiator system in the polymerizable monomers, andas a processing aid. Preferably, such solvents are not reactive withcomponents. It may be advantageous to prepare a concentrated solution ofthe transition metal complex in a small amount of solvent to simplifythe preparation of the polymerizable composition.

Suitable solvents include ethers such as diethyl ether, ethyl propylether, dipropyl ether, methyl t-butyl ether, di-t-butyl ether, glyme(dimethoxyethane), diglyme, diethylene glycol dimethyl ether; cyclicethers such as tetrahydrofuran and dioxane; alkanes; cycloalkanes;aromatic hydrocarbon solvents such as benzene, toluene, o-xylene,m-xylene, p-xylene; halogenated hydrocarbon solvents; acetonitrile;lactones such as butyrolactone, and valerolactones; ketones such asacetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone,and cyclohexanone; sulfones such as tetramethylene sulfone,3-methylsulfolane, 2,4-dimethylsulfolane, butadiene sulfone, methylsulfone, ethyl sulfone, propyl sulfone, butyl sulfone, methyl vinylsulfone, 2-(methylsulfonyl) ethanol, and 2,2′-sulfonyldiethanol;sulfoxides such as dimethyl sulfoxide; cyclic carbonates such aspropylene carbonate, ethylene carbonate and vinylene carbonate;carboxylic acid esters such as ethyl acetate, Methyl Cellosolve™ andmethyl formate; and other solvents such as methylene chloride,nitromethane, acetonitrile, glycol sulfite and 1,2-dimethoxyethane(glyme), mixtures of such solvents, and supercritical solvents (such asCO₂). The present polymerization may also be conducted in accordancewith known suspension, emulsion and precipitation polymerizationprocesses.

Preferably, the monomer(s) and components of the redox initiator systemare selected such that the rate of initiation is not less than 1,000times (preferably not less than 100 times) slower than the rate ofpropagation and/or transfer of the generated radical group to thepolymer radical. In the present application, “propagation” refers to thereaction of a polymer radical with a monomer to form a polymer-monomeradduct radicals.

Polymerizing may be conducted at a temperature of from −78 to 200° C.,preferably from 0 to 160° C. and most preferably from 20 to 100° C. Thereaction should be conducted for a length of time sufficient to convertat least 10% (preferably at least 50%, more preferably at least 75% andmost preferably at least 90%) of the monomer to polymer. Typically, thereaction time will be from several minutes to 5 days, preferably from 30minutes to 3 days, and most preferably from 1 to 24 hours.

Preferable the polymerizable composition comprises a “two-part” systemin which the polymerizable monomers and the transition metal complex arein the first mixture, and the oxidizing agent, the reducing agent andany fillers are in a second mixture. The two parts are combined,optionally coated on a substrate, and the redox initiated by exposure toactinic radiation.

The polymerizable composition and the redox initiator system may becombined may be irradiated with activating UV radiation to cleave orfragment the photolabile transition metal complex, initiate the redoxcycle and polymerize the polymerizable component(s). UV light sourcescan be of two types: 1) relatively low light intensity sources such asbacklights which provide generally 10 mW/cm² or less (as measured inaccordance with procedures approved by the United States NationalInstitute of Standards and Technology as, for example, with a Uvimap™ UM365 L-S radiometer manufactured by Electronic Instrumentation &Technology, Inc., in Sterling, Va.) over a wavelength range of 280 to400 nanometers and 2) relatively high light intensity sources such asmedium pressure mercury lamps which provide intensities generallygreater than 10 mW/cm², preferably between 15 and 450 mW/cm². Whereactinic radiation is used to fully or partially polymerize thepolymerizable composition, high intensities and short exposure times arepreferred. Intensities can range from about 0.1 to about 150 mW/cm²,preferably from about 0.5 to about 100 mW/cm², and more preferably fromabout 0.5 to about 50 mW/cm². UV LEDs may also be used, such as aClearstone UV LED lamp (Clearstone Technologies Inc., Hopkins, Minn. 385nm).

The above-described compositions may be coated on a substrate usingconventional coating techniques modified as appropriate to theparticular substrate. For example, these compositions can be applied toa variety of solid substrates by methods such as roller coating, flowcoating, dip coating, spin coating, spray coating, knife coating, anddie coating. These various methods of coating allow the compositions tobe placed on the substrate at variable thicknesses thus allowing a widerrange of use of the compositions.

The polymerizable compositions may be coated upon a variety of flexibleand inflexible substrates using conventional coating techniques toproduce coated articles. Flexible substrates are defined herein as anymaterial which is conventionally utilized as a tape backing or may be ofany other flexible material. Examples include, but are not limited toplastic films such as polypropylene, polyethylene, polyvinyl chloride,polyester (polyethylene terephthalate), polycarbonate, poly(methylmethacrylate) (PMMA), cellulose acetate, cellulose triacetate, and ethylcellulose. Foam backings may be used.

In some preferred embodiments, the substrate may be chosen so as to betransparent to the UV radiation used to initiate the redox cycle. Thecoated article may then be initiated through the thickness of thetransparent substrate. In other embodiments the substrate may be opaqueto the incident actinic radiation. The coated article having a layer ofthe polymerizable composition may be initiated before bond closure, andthe polymerization will continue once initiated.

The present disclosure further provides curable dental compositionscomprising the redox initiator system. Although various curable dentalcompositions have been described, industry would find advantage incompositions having improved properties such as improved working time,and reduced stress deflection and/or reduced shrinkage while maintainingsufficient mechanical properties and depth of cure.

As used herein, “dental composition” refers to a material, optionallycomprising filler, capable of adhering or being bonded to an oralsurface. A curable dental composition can be used to bond a dentalarticle to a tooth structure, form a coating (e.g., a sealant orvarnish) on a tooth surface, be used as a restorative that is placeddirectly into the mouth and cured in-situ, or alternatively be used tofabricate a prosthesis outside the mouth that is subsequently adheredwithin the mouth.

Curable dental compositions include, for example, adhesives (e.g.,dental and/or orthodontic adhesives), cements (e.g., resin-modifiedglass ionomer cements, and/or orthodontic cements), primers (e.g.,orthodontic primers), liners (applied to the base of a cavity to reducetooth sensitivity), coatings such as sealants (e.g., pit and fissure),and varnishes; and resin restoratives (also referred to as directcomposites) such as dental fillings, as well as crowns, bridges, andarticles for dental implants. Highly filled dental compositions are alsoused for mill blanks, from which a crown may be milled. A composite is ahighly filled paste designed to be suitable for filling substantialdefects in tooth structure. Dental cements are somewhat less filled andless viscous materials than composites, and typically act as a bondingagent for additional materials, such as inlays, onlays and the like, oract as the filling material itself if applied and cured in layers.Dental cements are also used for permanently bonding dental restorationssuch as a crown or bridge to a tooth surface or an implant abutment.

As used herein:

“dental article” refers to an article that can be adhered (e.g., bonded)to a tooth structure or dental implant. Dental articles include, forexample, crowns, bridges, veneers, inlays, onlays, fillings, orthodonticappliances and devices.

“orthodontic appliance” refers to any device intended to be bonded to atooth structure, including, but not limited to, orthodontic brackets,buccal tubes, lingual retainers, orthodontic bands, bite openers,buttons, and cleats. The appliance has a base for receiving adhesive andit can be a flange made of metal, plastic, ceramic, or combinationsthereof. Alternatively, the base can be a custom base formed from curedadhesive layer(s) (i.e. single or multi-layer adhesives).

“oral surface” refers to a soft or hard surface in the oral environment.Hard surfaces typically include tooth structure including, for example,natural and artificial tooth surfaces, bone, and the like.

“curable” is descriptive of a material or composition that can bepolymerized or crosslinked by a free radical means such as byirradiating with actinic irradiation to induce polymerization and/orcrosslinking; “hardened” refers to a material or composition that hasbeen cured (e.g., polymerized or crosslinked).

“initiator” refers to something that initiates curing of a resin. Aninitiator may include, for example, a polymerization initiator system, aphotoinitiator system, a thermal initiator and/or a redox initiatorsystem.

“self-etching” composition refers to a composition that bonds to adental structure surface without pretreating the dental structuresurface with an etchant. Preferably, a self-etching composition can alsofunction as a self-primer wherein no separate etchant or primer areused.

a “self-adhesive” composition refers to a composition that is capable ofbonding to a dental structure surface without pretreating the dentalstructure surface with a primer or bonding agent. Preferably, aself-adhesive composition is also a self-etching composition wherein noseparate etchant is used.

a “dental structure surface” refers to tooth structures (e.g., enamel,dentin, and cementum) and bone.

an “uncut” dental structure surface refers to a dental structure surfacethat has not been prepared by cutting, grinding, drilling, etc.

an “untreated” dental structure surface refers to a tooth or bonesurface that has not been treated with an etchant, primer, or bondingagent prior to application of a self-etching adhesive or a self-adhesivecomposition of the present invention.

an “unetched” dental structure surface refers to a tooth or bone surfacethat has not been treated with an etchant prior to application of aself-etching adhesive or a self-adhesive composition of the presentinvention.

The total amount of the redox initiator system in the polymerizableresin portion of the unfilled curable dental composition is typically nogreater than 5 wt. %. Generally, the amount of redox initiator system isfrom about 0.1 to 5 wt. % of the polymerizable portion of the unfilleddental composition.

The curable dental compositions comprise at least one ethylenicallyunsaturated resin monomer or oligomer in combination with the redoxinitiator system. In some embodiments, such as primers, theethylenically unsaturated monomer may be monofunctional, having a single(e.g. terminal) ethylenically unsaturated group. In other embodiments,such as dental restorations the ethylenically unsaturated monomer ismultifunctional. The phrase “multifunctional ethylenically unsaturated”means that the monomers each comprise at least two ethylenicallyunsaturated (e.g. free radically) polymerizable groups, such as(meth)acrylate groups.

The amount of curable resin in the dental composition is a function ofthe desired end use (adhesives, cements, restoratives, etc.) and can beexpressed with respect to the (i.e. unfilled) polymerizable resinportion of the dental composition. For favored embodiments, wherein thecomposition further comprises filler, the concentration of monomer canalso be expressed with respect to the total (i.e. filled) composition.When the composition is free of filler, the polymerizable resin portionis the same as the total composition.

In favored embodiments, such ethylenically unsaturated groups of thecurable dental resin includes (meth)acryloyl such as (meth)acrylamideand (meth)acrylate. Other ethylenically unsaturated polymerizable groupsinclude vinyl and vinyl ethers. The ethylenically unsaturated terminalpolymerizable group(s) is preferably a (meth)acrylate group,particularly for compositions that are hardened by exposure to actinic(e.g. UV and visible) radiation in the presence of the redox initiatorsystem. Further, methacrylate functionality is typically preferred overthe acrylate functionality in curable dental compositions. Theethylenically unsaturated monomer may comprise various ethylenicallyunsaturated monomers, as known in the art, for use in dentalcompositions.

In favored embodiments, the dental composition comprises one or moredental resins having a low volume shrinkage monomer. Preferred (e.g.filled) curable dental compositions (useful for restorations such asfillings and crowns) comprise one or more low volume shrinkage resinssuch that the composition exhibits a Watts Shrinkage of less than about2%, preferably no greater than 1.80%, more preferably no greater than1.60%. In favored embodiments, the Watts Shrinkage is no greater than1.50%, or no greater than 1.40%, or no greater than 1.30%, and in someembodiments no greater than 1.25%, or no greater than 1.20%, or nogreater than 1.15%, or no greater than 1.10%.

Preferred low volume shrinkage monomers include isocyanurate resins,such as described in U.S.S.N. 2013/0012614 (Abuelyaman et al.);tricyclodecane resins, such as described in U.S.S.N 2011/041736 (Eckertet al.); polymerizable resins having at least one cyclic allylic sulfidemoiety such as described in U.S. Pat. No. 7,888,400 (Abuelyaman et al.);methylene dithiepane silane resins as described in U.S. Pat. No.6,794,520 (Moszner et al.); and di-, tri, and/ortetra-(meth)acryloyl-containing resins such as described in U.S.2010/021869 (Abuelyaman et al.); each of which are incorporated hereinby reference.

In favored embodiments, the majority of the unfilled polymerizable resincomposition comprises one or more low volume shrinkage monomers (“Lowshrinkage monomers”). For example, at least 50%, 60%, 70%, 80%, 90% ormore of the unfilled polymerizable resin may comprise low volumeshrinkage monomer(s).

In one embodiment, the dental composition comprises at least oneisocyanurate resin. The isocyanurate resin comprises a trivalentisocyanuric acid ring as an isocyanurate core structure and at least twoethylenically unsaturated (e.g. free radically) polymerizable groupsbonded to at least two of the nitrogen atoms of the isocyanurate corestructure via a (e.g. divalent) linking group. The linking group is theentire chain of atoms between the nitrogen atom of the isocyanurate corestructure and the terminal ethylenically unsaturated group. Theethylenically unsaturated free radically polymerizable groups aregenerally bonded to the core or backbone unit via a (e.g. divalent)linking group.

The trivalent isocyanurate core structure generally has the formula:

The divalent linking group comprises at least one nitrogen, oxygen orsulfur atom. Such nitrogen, oxygen or sulfur atom forms a urethane,ester, thioester, ether, or thioether linkage. Ether and especiallyester linkages can be beneficial over isocyanurate resin comprisingurethane linkages for providing improved properties such as reducedshrinkage, and/or increased mechanical properties, e.g., diametraltensile strength (DTS). Thus, in some embodiments, the divalent linkinggroups of the isocyanurate resin are free of urethane linkages. In somefavored embodiments, the divalent linking group comprises an esterlinkage such as an aliphatic or aromatic diester linkage.

The isocyanurate monomer typically has the general structure:

wherein R⁷ is a (hetero)hydrocarbyl group including straight chain,branched or cyclic alkylene, arylene, or alkarylene, and optionallyincluding a heteroatom (e.g. oxygen, nitrogen, or sulfur); R⁴ ishydrogen or C1-C4 alkyl; R⁸ is heterohydrocarbyl group includingalkylene, arylene, or alkarylene linking group comprising at least onemoiety selected from urethane, ester, thioester, ether, or thioether,and combinations of such moieties; and at least one of the R⁹ groups is

R⁷ is typically a straight chain, branched or cyclic alkylene,optionally including a heteroatom, having no greater than 12 carbonsatoms. In some favored embodiments, R⁷ has no greater than 8, 6, or 4carbon atoms. In some favored embodiments, R₇ comprises at least onehydroxyl moiety.

In some embodiments, R⁸ comprises an aliphatic or aromatic ester linkagesuch as a diester linkage.

In some embodiment, R⁸ further comprises one or more ether moieties.Hence, the linking group may comprise a combination of ester or diestermoieties and one or more ether moieties.

For embodiments, wherein the isocyanurate monomer is a di(meth)acrylatemonomer, R⁹ is hydrogen, alkyl, aryl, or alkaryl, optionally including aheteroatom.

The polymerizable resin portion of the curable unfilled dentalcomposition described herein may comprise at least 10 wt. %, 15 wt. %,20 wt. %, or 25 wt. %, multifunctional ethylenically unsaturatedisocyanurate resin(s). The isocyanurate resin may comprise a singlemonomer or a blend of two or more isocyanurate resins. The total amountof isocyanurate resin(s) in the unfilled polymerizable resin portion ofthe curable dental composition is typically no greater than 90 wt. %, 85wt. %, 80 wt. %, or 75 wt. %.

The filled curable dental composition described herein typicallycomprises at least 5 wt. %, 6 wt. %, 7 wt. %, 8 wt. %, or 9 wt. % ofmultifunctional ethylenically unsaturated isocyanurate resin(s). Thetotal amount of isocyanurate resin(s) of the filled hardenable (i.e.polymerizable) dental composition is typically no greater than 20 wt. %,or 19 wt. %, or 18 wt. %, or 17 wt. %, or 16 wt. %, or 15 wt. %.

In another embodiment, the dental composition comprises at least onetricyclodecane resin. The tricyclodecane resin may comprise a singlemonomer or a blend of two or more tricyclodecane resins. Theconcentration of multifunctional ethylenically unsaturatedtricyclodecane monomer in the (i.e. unfilled) polymerizable resinportion or filled hardenable (i.e. polymerizable) composition can be thesame as just described for the multifunctional ethylenically unsaturatedisocyanurate monomer.

Tricyclodecane monomers generally have the core structure (i.e. backboneunit (U):

The backbone unit (U) if the tricyclodecane resin typically comprisesone or two spacer unit(s) (S) bonded to the backbone unit (U) via anether linkage. At least one spacer unit (S) comprises a CH(R¹⁰)—OGchain, wherein each group G comprises a (meth)acrylate moiety and R¹⁰(comprises at least one group selected from hydrogen, alkyl, aryl,alkaryl and combinations thereof. In some embodiments, R¹⁰ is hydrogen,methyl, phenyl, phenoxymethyl, and combinations thereof. G may be bondedto the spacer unit(s) (S) via a urethane moiety.

In some embodiments, the spacer unit(s) (S) typically comprise

wherein m is 1 to 3; n is 1 to 3; and R¹⁰ is hydrogen, methyl, phenyl,phenoxymethyl.

In other embodiments, the spacer unit(s) (S) typically comprise

wherein M=aryl.

In some embodiments the composition comprises a multifunctionalethylenically unsaturated isocyanurate monomer and multifunctionalethylenically unsaturated tricyclodecane monomer at a weight ratioranging from about 1.5:1 to 1:1.5.

In some embodiments, the curable dental composition comprises apolymerizable resin having at least one cyclic allylic sulfide moietywith at least one (meth)acryloyl moiety.

The cyclic allylic sulfide moiety typically comprises at least one 7- or8-membered ring that has two heteroatoms in the ring, one of which issulfur. Most typically both of the heteroatoms are sulfur, which mayoptionally be present as part of an SO, SO₂, or S—S moiety. In otherembodiments, the ring may comprise a sulfur atom plus a second,different heteroatom in the ring, such as oxygen or nitrogen. Inaddition, the cyclic allylic moiety may comprise multiple ringstructures, i.e. may have two or more cyclic allylic sulfide moieties.The (meth)acryloyl moiety is preferably a (meth)acryloyloxy (i.e. a(meth)acrylate moiety) or a (meth)acryloylamino (i.e., a(meth)acrylamide moiety).

In one embodiment, the low shrinkage resin includes those represented bythe formulae:

In the above formulae, each A can be independently selected from S, O,N, C (e.g., C(R¹⁰)₂, where each R¹⁰ is independently a H or an organicgroup), SO, SO₂, N-alkyl, N-acyl, NH, N-aryl, carboxyl or carbonylgroup, provided that at least one X is S or a group comprising S.Preferably, each A is sulfur.

B is either alkylene (e.g., methylene, ethylene, etc.) optionallyincluding a heteroatom, carbonyl, or acyl; or is absent, therebyindicating the size of the ring, typically 7- to 10-membered rings,however larger rings are also contemplated. Preferably, the ring iseither a 7- or 8-membered ring with B thus being either absent ormethylene, respectively. In some embodiments, B is either absent or is aC1 to C3 alkylene, optionally including a heteroatom, carbonyl, acyl, orcombinations thereof.

X¹ is independently —O— or —NR⁴—, where R⁴ is H or C1-C4 alkyl.

The R¹¹ group represents a linker selected from alkylene (typicallyhaving more than one carbon atom, i.e. excluding methylene), alkyleneoptionally including a heteroatom (e.g., O, N, S, S—S, SO, SO₂),arylene, cycloaliphatic, carbonyl, siloxane, amido (—CO—NH—), acyl(—CO—O—), urethane (—O—CO—NH—), and urea (—NH—CO—NH—) groups, andcombinations thereof. In certain embodiments, R′ comprises an alkylenegroup, typically a methylene or longer group, that may be eitherstraight chain or branched, and which can be either unsubstituted, orsubstituted with aryl, cycloalkyl, halogen, nitrile, alkoxy, alkylamino,dialkylamino, akylthio, carbonyl, acyl, acyloxy, amido, urethane group,urea group, a cyclic allylic sulfide moiety, or combinations thereof.

R⁴ is H or C₁-C₄ alkyl, and “a” and “b” are independently 1 to 3.

Optionally the cyclic allylic sulfide moiety can further be substitutedon the ring with one or more groups selected from straight or branchedchain alkyl, aryl, cycloalkyl, halogen, nitrile, alkoxy, alkylamino,dialkylamino, akylthio, carbonyl, acyl, acyloxy, amido, urethane group,and urea group. Preferably the selected substituents do not interferewith the hardening reaction. Preferred are cyclic allylic sulfidestructures that comprise unsubstituted methylene members.

A typical low shrinkage monomer can comprise an 8-membered cyclicallylic sulfide moiety with two sulfur atoms in the ring and with thelinker attached directly to the 3-position of the ring with an acylgroup (i.e., Ring-OC(O)—). Typically the weight average molecular weight(MW) of the hybrid monomer ranges from about 400 to about 900 and insome embodiments is at least 250, more typically at least 500, and mosttypically at least 800.

The inclusion of a polymerizable compound having at least one cyclicallylic sulfide moiety can result in a synergistic combination of lowvolume shrinkage in combination with high diametral tensile strength.

In another embodiment, the dental composition comprises a low shrinkageresin that includes at least one di-, tri-, and/or tetra(meth)acryloyl-containing resins having the general formula:

wherein: each X¹ is independently —O— or —NR⁴—, where R⁴ is H or C₁-C₄alkyl; D and E each independently represent an organic group, and R¹²represents —C(O)C(CH₃)═CH₂, and/or p=0 and R¹² represents H,—C(O)CH═CH₂, or —C(O)C(CH₃)═CH₂, with the proviso that at least one R¹²is a (meth)acrylate; each m is 1 to 5; p and q are independently 0 or 1.Although this material is a derivative of bisphenol A, when other lowvolume shrinkage monomer are employed, such as the isocyanurate and/ortricyclodecane monomer, the dental composition is free of (meth)acrylatemonomers derived from bisphenol A. Such resins are described in WO2008/082881 (Abuelyaman et al.)

In another embodiment, the low shrinkage dental resin may be selectedfrom methylene dithiepane silane resins described in U.S. Pat. No.6,794,520 (Moszner et al.), incorporated herein by reference. Suchresins have the general formula

in which R¹⁴ is a saturated or unsaturated aliphatic or alicyclichydrocarbon radical with 1 to 10 carbon atoms, which can be interruptedby one or more oxygen and/or sulfur atoms and can contain one or moreester, carbonyl, amide and/or urethane groups, or is an aromatic orheteroaromatic hydrocarbon radical with 6 to 18 carbon atoms, thehydrocarbon radicals being able to be substituted or unsubstituted; R¹⁵has one of the meanings given for R¹⁴ or is absent; R¹⁶ has one of themeanings given for R¹⁴ or is absent; R¹⁷ is equal to —(CHR¹⁹)_(n)—,—W—CO—NH—(CHR¹⁹)_(n)—, —(CHR¹⁹)_(n), —SR¹⁸—, —CO—O—R¹⁸— or is absent,with n being equal to 1 to 4, R¹⁹ is hydrogen, C₁ to C₁₀ alkyl or C₆ toC₁₀ aryl, R¹⁸ has one of the meanings given for R¹⁴ and W stands for anO or S atom or is absent; with R¹⁸ and R¹⁹ being able to be substitutedor unsubstituted; R²⁰ is a hydrolyzable group; d, e, f and x eachindependently of each other being 1, 2 or 3; and the sum of d+x=2 to 4.

The multifunctional low shrinkage resins are (e.g. highly) viscousliquids at about 25° C., yet are flowable. The viscosity as can bemeasured with a Haake RotoVisco RV1 device, as described in EPApplication No. 10168240.9, filed Jul. 2, 2010 is typically at least300, or 400, or 500 Pa*s and no greater than 10,000 Pascal-seconds(Pa*s). In some embodiments, the viscosity is no greater than 5000 or2500 Pa*s.

The ethylenically unsaturated resins of the dental composition aretypically stable liquids at about 25° C. meaning that the resins do notsubstantially polymerize, crystallize, or otherwise solidify when storedat room temperature (about 25° C.) for a typical shelf life of at least30, 60, or 90 days. The viscosity of the resins typically does notchange (e.g. increase) by more than 10% of the initial viscosity.

Particularly for dental restoration compositions, the ethylenicallyunsaturated resins generally have a refractive index of at least 1.50.In some embodiments, the refractive index is at least 1.51, 1.52, 1.53,or greater. The inclusion of sulfur atoms and/or the present of one ormore aromatic moieties can raise the refractive index (relative to thesame molecular weight resin lacking such substituents).

In some embodiments, the (unfilled) polymerizable resin may comprisesolely one or more low shrink resins in combination with the redoxinitiator system. In other embodiments, the (unfilled) polymerizableresin comprises a small concentration of other monomer(s). By “other” isit meant an ethylenically unsaturated monomer such as a (meth)acrylatemonomer that is not a low volume shrinkage monomer.

The concentration of such other monomer(s) is typically no greater than20 wt. %, 19 wt. %, 18 wt. %, 17 wt. %, 16 wt. %, or 15 wt. % of the(unfilled) polymerizable resin portion. The concentration of such othermonomers is typically no greater than 5 wt. %, 4 wt. %, 3 wt. %, or 2wt. % of the filled polymerizable dental composition.

In some embodiments, the “other monomers” of the dental compositioncomprise a low viscosity reactive (i.e. polymerizable) diluent. Reactivediluents typically have a viscosity of no greater than 300 Pa*s andpreferably no greater than 100 Pa*s, or 50 Pa*s, or 10 Pa*s. In someembodiments, the reactive diluent has a viscosity no greater than 1 or0.5 Pa*s. Reactive diluents are typically relatively low in molecularweight, having a molecular weight less than 600 g/mole, or 550 g/mol, or500 g/mole. Reactive diluents typically comprise one or twoethylenically unsaturated groups such as in the case ofmono(meth)acrylate or di(meth)acrylate monomers.

In some embodiments, the reactive diluent is an isocyanurate ortricyclodecane monomer. Tricyclodecane reactive diluent may have thesame generally structure as previously described. In favoredembodiments, the tricyclodecane reactive diluent comprises one or twospacer unit(s) (S) being connected to the backbone unit (U) via an etherlinkage; such as described in U.S. 2011/041736 (Eckert et al.);incorporated herein by reference.

The curable component of the curable dental composition can include awide variety of “other” ethylenically unsaturated compounds (with orwithout acid functionality), epoxy-functional (meth)acrylate resins,vinyl ethers, and the like.

The dental compositions may include free radically polymerizablemonomers, agents, and polymers having one or more ethylenicallyunsaturated groups. Suitable compounds contain at least oneethylenically unsaturated bond and are capable of undergoing additionpolymerization. Examples of useful ethylenically unsaturated compoundsinclude acrylic acid esters, methacrylic acid esters, hydroxy-functionalacrylic acid esters, hydroxy-functional methacrylic acid esters, andcombinations thereof.

Such free radically polymerizable compounds include mono-, di- orpoly-(meth)acrylates (i.e., acrylates and methacrylates) such as, methyl(meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-hexyl(meth)acrylate, stearyl (meth)acrylate, allyl (meth)acrylate, glyceroltri(meth)acrylate, ethyleneglycol di(meth)acrylate, diethyleneglycoldi(meth)acrylate, triethyleneglycol di(meth)acrylate, 1,3-propanedioldi(meth)acrylate, trimethylolpropane tri(meth)acrylate,1,2,4-butanetriol tri(meth)acrylate, 1,4-cyclohexanedioldi(meth)acrylate, pentaerythritol tetra(meth)acrylate, sorbitolhex(meth)acrylate, tetrahydrofurfuryl (meth)acrylate,bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylmethane,bis[1-(3-acryloxy-2-hydroxy)]-p-propoxyphenyldimethylmethane,ethoxylated bisphenol A di(meth)acrylate, andtrishydroxyethyl-isocyanurate tri(meth)acrylate; (meth)acrylamides(i.e., acrylamides and methacrylamides) such as (meth)acrylamide,methylene bis-(meth)acrylamide, and diacetone (meth)acrylamide; urethane(meth)acrylates; the bis-(meth)acrylates of polyethylene glycols(preferably of molecular weight 200-500); and vinyl compounds such asstyrene, diallyl phthalate, divinyl succinate, divinyl adipate anddivinyl phthalate. Other suitable free radically polymerizable compoundsinclude siloxane-functional (meth)acrylates. Mixtures of two or morefree radically polymerizable compounds can be used if desired.

The curable dental composition may also contain a monomer havinghydroxyl groups and ethylenically unsaturated groups as an example of an“other monomer”. Examples of such materials include hydroxyalkyl(meth)acrylates, such as 2-hydroxyethyl (meth)acrylate and2-hydroxypropyl (meth)acrylate; glycerol mono- or di-(meth)acrylate;trimethylolpropane mono- or di-(meth)acrylate; pentaerythritol mono-,di-, and tri-(meth)acrylate; sorbitol mono-, di-, tri-, tetra-, orpenta-(meth)acrylate; and2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (bisGMA).Suitable ethylenically unsaturated compounds are available from a widevariety of commercial sources, such as Sigma-Aldrich, St. Louis.

The curable dental compositions can include at least 1 wt. %, at least 3wt. %, or at least 5 wt. % ethylenically unsaturated compounds withhydroxyl functionality, based on the total weight of the unfilledcomposition. The compositions can include at most 80 wt. %, at most 70wt. %, or at most 60 wt. % ethylenically unsaturated compounds withhydroxyl functionality.

The dental compositions described herein may include one or more curablecomponents in the form of ethylenically unsaturated compounds with acidfunctionality as an example of an “other” monomer. When present, thepolymerizable component optionally comprises an ethylenicallyunsaturated compound with acid functionality. Preferably, the acidfunctionality includes an oxyacid (i.e., an oxygen-containing acid) ofcarbon, sulfur, phosphorous, or boron. Such acid-functional “other”monomers contribute to the self-adhesion or self-etching of the dentalcompositions as described in U.S. 2005/017966 (Falsafi et al.),incorporated herein by reference.

As used herein, ethylenically unsaturated compounds with acidfunctionality is meant to include monomers, oligomers, and polymershaving ethylenic unsaturation and acid and/or acid-precursorfunctionality. Acid-precursor functionalities include, for example,anhydrides, acid halides, and pyrophosphates. The acid functionality caninclude carboxylic acid functionality, phosphoric acid functionality,phosphonic acid functionality, sulfonic acid functionality, orcombinations thereof.

Ethylenically unsaturated compounds with acid functionality include, forexample, α,β-unsaturated acidic compounds such as glycerol phosphatemono(meth)acrylates, glycerol phosphate di(meth)acrylates, hydroxyethyl(meth)acrylate (e.g., HEMA) phosphates, bis((meth)acryloxyethyl)phosphate, bis((meth)acryloxypropyl) phosphate,bis((meth)acryloxy)propyloxy phosphate, (meth)acryloxyhexyl phosphate,bis((meth)acryloxyhexyl) phosphate, (meth)acryloxyoctyl phosphate,bis((meth)acryloxyoctyl) phosphate, (meth)acryloxydecyl phosphate,bis((meth)acryloxydecyl) phosphate, caprolactone methacrylate phosphate,citric acid di- or tri-methacrylates, poly(meth)acrylated oligomaleicacid, poly(meth)acrylated polymaleic acid, poly(meth)acrylatedpoly(meth)acrylic acid, poly(meth)acrylated polycarboxyl-polyphosphonicacid, poly(meth)acrylated polychlorophosphoric acid, poly(meth)acrylatedpolysulfonate, poly(meth)acrylated polyboric acid, and the like, may beused as components. Also, monomers, oligomers, and polymers ofunsaturated carbonic acids such as (meth)acrylic acids, itaconic acid,aromatic (meth)acrylated acids (e.g., methacrylated trimellitic acids),and anhydrides thereof can be used.

The dental compositions can include an ethylenically unsaturatedcompound with acid functionality having at least one P—OH moiety. Suchcompositions are self-adhesive and are non-aqueous. For example, suchcompositions can include: a first compound including at least one(meth)acryloxy group and at least one —O—P(O)(OH)_(x) group, wherein x=1or 2, and wherein the at least one —O—P(O)(OH)_(x) group and the atleast one (meth)acryloxy group are linked together by a C₁-C₄hydrocarbon group; a second compound including at least one(meth)acryloxy group and at least one —O—P(O)(OH)_(x) group, wherein x=1or 2, and wherein the at least one —O—P(O)(OH)_(x) group and the atleast one (meth)acryloxy group are linked together by a C₅-C₁₂hydrocarbon group; an ethylenically unsaturated compound without acidfunctionality; an initiator system; and a filler.

The curable dental compositions can include at least 1 wt. %, at least 3wt. %, or at least 5 wt. % ethylenically unsaturated compounds with acidfunctionality, based on the total weight of the unfilled composition.The compositions can include at most 80 wt. %, at most 70 wt. %, or atmost 60 wt. % ethylenically unsaturated compounds with acidfunctionality.

The curable dental compositions may include resin-modified glass ionomercements such as those described in U.S. Pat. No. 5,130,347 (Mitra), U.S.Pat. No. 5,154,762 (Mitra), U.S. Pat. No. 5,925,715 (Mitra et al.) andU.S. Pat. No. 5,962,550 (Akahane). Such compositions can bepowder-liquid, paste-liquid or paste-paste systems. Alternatively,copolymer formulations such as those described in U.S. Pat. No.6,126,922 (Rozzi) are contemplated.

The curable dental compositions include the redox cure systems thatinclude a polymerizable component (e.g., an ethylenically unsaturatedpolymerizable component including monomers and oligomers) and redoxagents that include an oxidizing agent, a reducing agent and thephotolabile transition metal complex.

The photolabile transition metal complex, and the reducing and oxidizingagents react with or otherwise cooperate with one another to producefree radicals capable of initiating polymerization of the resin system(e.g., the ethylenically unsaturated component). Once initiated, thistype of cure is not dependent on continued irradiation and can proceedin the absence of light. The reducing and oxidizing agents arepreferably sufficiently shelf-stable and free of undesirablecolorization to permit their storage and use under typical conditions.

Useful reducing agents include ascorbic acid, ascorbic acid derivatives,and metal complexed ascorbic acid compounds as described in U.S. Pat.No. 5,501,727 (Wang et al.); amines, especially tertiary amines, such as4-tert-butyl dimethylaniline; aromatic sulfinic salts, such asp-toluenesulfinic salts and benzenesulfinic salts; thioureas, such as1-ethyl-2-thiourea, tetraethyl thiourea, tetramethyl thiourea,1,1-dibutyl thiourea, and 1,3-dibutyl thiourea; and mixtures thereof.Other secondary reducing agents may include cobalt (II) chloride,ferrous chloride, ferrous sulfate, hydrazine, hydroxylamine (dependingon the choice of oxidizing agent), salts of a dithionite or sulfiteanion, and mixtures thereof. Preferably, the reducing agent is anascorbic acid derivative.

Suitable oxidizing agents will also be familiar to those skilled in theart, and include but are not limited to persulfuric acid and saltsthereof, such as sodium, potassium, ammonium, cesium, and alkyl ammoniumsalts. Preferable oxidizing agents include peroxides such as benzoylperoxides, hydroperoxides such as cumyl hydroperoxide, t-butylhydroperoxide, and amyl hydroperoxide, as well as salts of transitionmetals such as cobalt (III) chloride and ferric chloride, cerium (IV)sulfate, perboric acid and salts thereof, permanganic acid and saltsthereof, perphosphoric acid and salts thereof, and mixtures thereof.

It may be desirable to use more than one oxidizing agent or more thanone reducing agent.

The photolabile transition metal complex is added to accelerate the rateof redox cure, improve the working time, and simplify the compounding ofthe dental resin so that the reaction is initiated or accelerated onlyupon exposure to actinic radiation that photolyzes the complex andinitiates polymerization.

The reducing or oxidizing agents can be microencapsulated as describedin U.S. Pat. No. 5,154,762 (Mitra et al.). This will generally enhanceshelf stability of the polymerizable composition, and if necessarypermit packaging the reducing and oxidizing agents together. Forexample, through appropriate selection of an encapsulant, the oxidizingand reducing agents can be combined with an acid-functional componentand optional filler and kept in a storage-stable state. The redoxinitiator is used in an amount effective to facilitate free radicaladdition of the polymerizable components, and the molecular weight ofthe polymer and the degree of functionalization desired. The initiatorsystem can be used in amounts from about 0.1 part by weight to about 5parts by weight based on 100 parts total monomer.

The photopolymerizable compositions are typically prepared by admixingthe various components of the compositions. For embodiments wherein thephotopolymerizable compositions are not cured in the presence of air,the initiator system is combined under “safe light” conditions (i.e.,conditions that do not cause premature hardening of the composition).Suitable inert solvents may be employed if desired when preparing themixture.

Curing is effected by exposing the composition to a radiation source,preferably a UV light source. It is convenient to employ light sourcesthat emit actinic radiation light between 320 nm and 400 nm(particularly blue light of a wavelength of 380-520 nm) such as quartzhalogen lamps, tungsten-halogen lamps, mercury arcs, carbon arcs, low-,medium-, and high-pressure mercury lamps, plasma arcs, light emittingdiodes, and lasers. In general, useful light sources have intensities inthe range of 500-1500 mW/cm². A variety of conventional lights can beused, including UV LEDs, for curing such compositions.

The exposure may be accomplished in several ways. Although thepolymerizable composition may be continuously exposed to radiationthroughout the entire hardening process (e.g., about 2 seconds to about60 seconds), the instant initiator system allows one to expose thecomposition to a single dose of radiation, and then remove the radiationsource, thereby allowing polymerization to occur.

In favored embodiments, such as when the dental composition is employedas a dental restorative (e.g. dental filling or crown) or an orthodonticcement, the dental composition typically comprises appreciable amountsof (e.g. nanoparticle) filler. The amount of such fillers is a functionof the end use as further described herein. Such compositions preferablyinclude at least 40 wt. %, more preferably at least 45 wt. %, and mostpreferably at least 50 wt. % filler, based on the total weight of thecomposition. In some embodiments the total amount of filler is at most90 wt. %, preferably at most 80 wt. %, and more preferably at most 75wt. % filler.

The filled dental composite materials typically exhibit a diametraltensile strength (DTS) of at least about 70, 75, or 80 MPa and/or aBarcol Hardness of at least about 60, or 65, or 70. The ISO 4049 depthof cure ranges from about 4 to about 5 mm and is comparable tocommercially available (e.g. filled) dental compositions suitable forrestorations.

Dental compositions suitable for use as dental adhesives can optionallyalso include filler in an amount of at least 1 wt. %, 2 wt. %, 3 wt. %,4 wt. %, or 5 wt. % based on the total weight of the composition. Forsuch embodiments, the total concentration of filler is at most 40 wt. %,preferably at most 20 wt. %, and more preferably at most 15 wt. %filler, based on the total weight of the composition.

Fillers may be selected from one or more of a wide variety of materialssuitable for incorporation in compositions used for dental applications,such as fillers currently used in dental restorative compositions, andthe like.

The filler can be an inorganic material. It can also be a crosslinkedorganic material that is insoluble in the polymerizable resin, and isoptionally filled with inorganic filler. The filler is generallynon-toxic and suitable for use in the mouth. The filler can beradiopaque, radiolucent, or nonradiopaque. Fillers as used in dentalapplications are typically ceramic in nature.

Suitable inorganic filler particles include quartz (i.e., silica),submicron silica, zirconia, submicron zirconia, and non-vitreousmicroparticles of the type described in U.S. Pat. No. 4,503,169(Randklev).

The filler can also be an acid-reactive filler. Suitable acid-reactivefillers include metal oxides, glasses, and metal salts. Typical metaloxides include barium oxide, calcium oxide, magnesium oxide, and zincoxide. Typical glasses include borate glasses, phosphate glasses, andfluoroaluminosilicate (“FAS”) glasses. The FAS glass typically containssufficient elutable cations so that a hardened dental composition willform when the glass is mixed with the components of the hardenablecomposition. The glass also typically contains sufficient elutablefluoride ions so that the hardened composition will have cariostaticproperties. The glass can be made from a melt containing fluoride,alumina, and other glass-forming ingredients using techniques familiarto those skilled in the FAS glassmaking art. The FAS glass typically isin the form of particles that are sufficiently finely divided so thatthey can conveniently be mixed with the other cement components and willperform well when the resulting mixture is used in the mouth.

Generally, the average particle size (typically, diameter) for the FASglass is no greater than 12 micrometers, typically no greater than 10micrometers, and more typically no greater than 5 micrometers asmeasured using, for example, a sedimentation particle size analyzer.Suitable FAS glasses will be familiar to those skilled in the art, andare available from a wide variety of commercial sources, and many arefound in currently available glass ionomer cements such as thosecommercially available under the trade designations VITREMER, VITREBOND,RELY X LUTING CEMENT, RELY X LUTING PLUS CEMENT, PHOTAC-FIL QUICK,KETAC-MOLAR, and KETAC-FIL PLUS (3M ESPE Dental Products, St. Paul,Minn.), FUJI II LC and FUJI IX (G-C Dental Industrial Corp., Tokyo,Japan) and CHEMFIL Superior (Dentsply International, York, Pa.).Mixtures of fillers can be used if desired.

Other suitable fillers are disclosed in U.S. Pat. No. 6,387,981 (Zhanget al.) and U.S. Pat. No. 6,572,693 (Wu et al.) as well as PCTInternational Publication Nos. WO 01/30305 (Zhang et al.), U.S. Pat. No.6,730,156 (Windisch et al.), WO 01/30307 (Zhang et al.), and WO03/063804 (Wu et al.). Filler components described in these referencesinclude nanosized silica particles, nanosized metal oxide particles, andcombinations thereof. Nanofillers are also described in U.S. Pat. No.7,090,721 (Craig et al.), U.S. Pat. No. 7,090,722 (Budd et al.) and U.S.Pat. No. 7,156,911; and 7,649,029 (Kolb et al.).

Examples of suitable organic filler particles include filled or unfilledpulverized polycarbonates, polyepoxides, poly(meth)acrylates and thelike. Commonly employed dental filler particles are quartz, submicronsilica, and non-vitreous microparticles of the type described in U.S.Pat. No. 4,503,169 (Randklev).

Mixtures of these fillers can also be used, as well as combinationfillers made from organic and inorganic materials.

Fillers may be either particulate or fibrous in nature. Particulatefillers may generally be defined as having a length to width ratio, oraspect ratio, of 20:1 or less, and more commonly 10:1 or less. Fiberscan be defined as having aspect ratios greater than 20:1, or morecommonly greater than 100:1. The shape of the particles can vary,ranging from spherical to ellipsoidal, or more planar such as flakes ordiscs. The macroscopic properties can be highly dependent on the shapeof the filler particles, in particular the uniformity of the shape.

Micron-size particles are very effective for improving post-cure wearproperties. In contrast, nanoscopic fillers are commonly used asviscosity and thixotropy modifiers. Due to their small size, highsurface area, and associated hydrogen bonding, these materials are knownto assemble into aggregated networks.

In some embodiments, the dental composition preferably comprises ananoscopic particulate filler (i.e., a filler that comprisesnanoparticles) having an average primary particle size of less thanabout 0.100 micrometers (i.e., microns), and more preferably less than0.075 microns. As used herein, the term “primary particle size” refersto the size of a non-associated single particle. The average primaryparticle size can be determined by cutting a thin sample of hardeneddental composition and measuring the particle diameter of about 50-100particles using a transmission electron micrograph at a magnification of300,000 and calculating the average. The filler can have a unimodal orpolymodal (e.g., bimodal) particle size distribution. The nanoscopicparticulate material typically has an average primary particle size ofat least about 2 nanometers (nm), and preferably at least about 7 nm.Preferably, the nanoscopic particulate material has an average primaryparticle size of no greater than about 75 nm, and more preferably nogreater than about 20 nm in size. The average surface area of such afiller is preferably at least about 20 square meters per gram (m²/g),more preferably, at least about 50 m²/g, and most preferably, at leastabout 100 m²/g.

In some preferred embodiments, the dental composition comprises silicananoparticles. Suitable nano-sized silicas are commercially availablefrom Nalco Chemical Co. (Naperville, Ill.) under the product designationNALCO COLLOIDAL SILICAS. For example, preferred silica particles can beobtained from using NALCO products 1040, 1041, 1042, 1050, 1060, 2327and 2329.

Silica particles are preferably made from an aqueous colloidaldispersion of silica (i.e., a sol or aquasol). The colloidal silica istypically in the concentration of about 1 to 50 weight percent in thesilica sol. Colloidal silica sols that can be used are availablecommercially having different colloid sizes, see Surface & ColloidScience, Vol. 6, ed. Matijevic, E., Wiley Interscience, 1973. Preferredsilica sols for use making the fillers are supplied as a dispersion ofamorphous silica in an aqueous medium (such as the Nalco colloidalsilicas made by Nalco Chemical Company) and those which are low insodium concentration and can be acidified by admixture with a suitableacid (e.g. Ludox colloidal silica made by E.I. Dupont de Nemours & Co.or Nalco 2326 from Nalco Chemical Co.).

Preferably, the silica particles in the sol have an average particlediameter of about 5-100 nm, more preferably 10-50 nm, and mostpreferably 12-40 nm. A particularly preferred silica sol is NALCO™ 1042or 2327.

In some embodiments, the dental composition comprises zirconiananoparticles. Suitable nano-sized zirconia nanoparticles can beprepared using hydrothermal technology as described in U.S. Pat. No.7,241,437 (Davidson et al.).

In some embodiments, lower refractive index (e.g. silica) nanoparticlesare employed in combination with high refractive index (e.g. zirconia)nanoparticles in order to index match (refractive index within 0.02) thefiller to the refractive index of the polymerizable resin.

In some embodiments, the nanoparticles are in the form of nanoclusters,i.e. a group of two or more particles associated by relatively weakintermolecular forces that cause the particles to clump together, evenwhen dispersed in a hardenable resin.

Preferred nanoclusters can comprise a substantially amorphous cluster ofnon-heavy (e.g. silica) particles, and amorphous heavy metal oxide (i.e.having an atomic number greater than 28) particles such as zirconia. Theprimary particles of the nanocluster preferably have an average diameterof less than about 100 nm. Suitable nanocluster fillers are described inU.S. Pat. No. 6,730,156 (Windisch et al.); incorporated herein byreference.

In some preferred embodiments, the dental composition comprisesnanoparticles and/or nanoclusters surface treated with an organometalliccoupling agent to enhance the bond between the filler and the resin. Theorganometallic coupling agent may be functionalized with reactive curinggroups, such as acrylates, methacrylates, vinyl groups and the like andmay comprise silane, zirconate or titanate coupling agents. Preferredcoupling agents include gamma-methacryloxypropyltrimethoxysilane,gamma-mercaptopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane,and the like.

Suitable copolymerizable or reactive organometallic compounds may havethe general formulas: CH₂═C(R²²)—R²¹Si(OR)_(n)R_(3-n) orCH₂═C(R²²)—C═OOR²¹Si(OR)_(n)R_(3-n); wherein R is an C₁-C₄ alkyl, R²¹ isa divalent organic heterohydrocarbyl linking group, preferably alkylene;R²² is H or C1-C4 alkyl; and n is from 1 to 3. Preferred coupling agentsinclude gamma-methacryloxypropyltrimethoxysilane,gamma-mercaptopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane,and the like.

In some embodiments, the disclosure provides a universal restorativecomposite comprising:

a) 15-30 wt. % of a curable dental resin comprising at least twopolymerizable, ethylenically unsaturated groups;

b) 70-85 wt. % of an inorganic filler, preferably a surface modifiedfiller;

c) 0.1 to 5 wt. % of the redox initiator system, relative to 100 partsby weight a).

In some embodiments, the disclosure provides a flowable restorative(flowable) composite comprising:

a) 25-50 wt. % of a curable dental resin comprising at least twopolymerizable, ethylenically unsaturated groups;

b) 30-75 wt. % of an inorganic filler, preferably a surface modifiedfiller;

c) 0.1 to 5 wt. % of the redox initiator system, relative to 100 partsby weight of a), said curable composition further comprising aninitiator and <2% stabilizers, pigments, etc.

In some embodiments, the disclosure provides a resin modifiedglass-ionomer adhesive comprising:

-   -   a) 10-25 wt. % of a partially (meth)acrylated poly(meth) acrylic        acid, which includes acrylic acids such as itaconic acid;    -   b) 5-20 wt. % of a hydroxyalkyl (meth)acrylate;    -   c) 30-60 wt. % of fluoroaluminosilicate (FAS) acid reactive        glass    -   d) 0-20 wt. % non-acid reactive fillers, preferably        surface-treated;    -   e) 10-20 wt. % water; and    -   f) 0.1 to 5 wt. % of the redox initiator system, relative to 100        parts by weight of a)-c)    -   said curable composition further comprising an initiator and <2%        stabilizers, or pigments.

Preferably the fluoroaluminosilicate is a silane methacrylatesurface-treated fluoroaluminosilicate.

In some embodiments, the disclosure provides a dental adhesivecomprising:

a) 30-80 wt. % mono (meth)acrylate monomers;

b) 1-10 wt. % polyfunctional (meth)acrylate monomers;

c) 5-60 wt. % monomers having an acid-functional group (includingphosphate, phosphonate, carboxylate, sulfonic acids)

d) 0-10, preferably 1-10 wt. % poly(meth)acrylic acid methacrylatemonomers;

e) 0.1 to 5 wt. % of the redox initiator system, relative to 100 partsby weight of a) to d)

f) 0-30 wt. % inorganic filler, preferably surface modified, relative to100 parts by weight of a) to d);

g) 0 to 25 wt. % solvent relative to 100 parts by weight of a) to d);

h) 0 to 25 wt. % water relative to 100 parts by weight of a) to d); and

<2% stabilizers, pigments.

In some embodiments, the dental compositions can have an initial colordifferent than the cured dental structures. Color can be imparted to thecomposition through the use of a photobleachable or thermochromic dye.As used herein, “photobleachable” refers to loss of color upon exposureto actinic radiation. The composition can include at least 0.001 wt. %photobleachable or thermochromic dye, and typically at least 0.002 wt. %photobleachable or thermochromic dye, based on the total weight of thecomposition. The composition typically includes at most 1 wt. %photobleachable or thermochromic dye, and more typically at most 0.1 wt.% photobleachable or thermochromic dye, based on the total weight of thecomposition. The amount of photobleachable and/or thermochromic dye mayvary depending on its extinction coefficient, the ability of the humaneye to discern the initial color, and the desired color change. Suitablethermochromic dyes are disclosed, for example, in U.S. Pat. No.6,670,436 (Burgath et al.).

For embodiments including a photobleachable dye, the color formation andbleaching characteristics of the photobleachable dye varies depending ona variety of factors including, for example, acid strength, dielectricconstant, polarity, amount of oxygen, and moisture content in theatmosphere. However, the bleaching properties of the dye can be readilydetermined by irradiating the composition and evaluating the change incolor. The photobleachable dye is generally at least partially solublein a hardenable resin.

Photobleachable dyes include, for example, Rose Bengal, MethyleneViolet, Methylene Blue, Fluorescein, Eosin Yellow, Eosin Y, Ethyl Eosin,Eosin Bluish, Eosin B, Erythrosin B, Erythrosin Yellowish Blend,Toluidine Blue, 4′,5′-Dibromofluorescein, and combinations thereof.

The color change can be initiated by actinic radiation such as providedby a dental curing light which emits visible or near infrared (IR) lightfor a sufficient amount of time. The mechanism that initiates the colorchange in the compositions may be separate from or substantiallysimultaneous with the hardening mechanism that hardens the resin. Forexample, a composition may harden when polymerization is initiatedchemically (e.g., redox initiation) or thermally, and the color changefrom an initial color to a final color may occur subsequent to thehardening process upon exposure to actinic radiation.

Optionally, compositions may contain solvents (e.g., alcohols (e.g.,propanol, ethanol), ketones (e.g., acetone, methyl ethyl ketone), esters(e.g., ethyl acetate), other nonaqueous solvents (e.g.,dimethylformamide, dimethylacetamide, dimethylsulfoxide,1-methyl-2-pyrrolidinone)), and water.

If desired, the compositions can contain additives such as indicators,dyes, pigments, inhibitors, accelerators, viscosity modifiers, wettingagents, buffering agents, radical and cationic stabilizers (for exampleBHT,), and other similar ingredients that will be apparent to thoseskilled in the art.

Additionally, medicaments or other therapeutic substances can beoptionally added to the dental compositions. Examples include, but arenot limited to, fluoride sources, whitening agents, anticaries agents(e.g., xylitol), calcium sources, phosphorus sources, remineralizingagents (e.g., calcium phosphate compounds), enzymes, breath fresheners,anesthetics, clotting agents, acid neutralizers, chemotherapeuticagents, immune response modifiers, thixotropes, polyols,anti-inflammatory agents, antimicrobial agents, antifungal agents,agents for treating xerostomia, desensitizers, and the like, of the typeoften used in dental compositions. Combinations of any of the aboveadditives may also be employed. The selection and amount of any one suchadditive can be selected by one of skill in the art to accomplish thedesired result without undue experimentation.

The curable dental composition can be used to treat an oral surface suchas tooth, as known in the art. In some embodiments, the compositions canbe hardened by curing after applying the dental composition. Forexample, when the curable dental composition is used as a restorativesuch as a dental filling, the method generally comprises applying thecurable composition to an oral surface (e.g. cavity); and curing thecomposition. In some embodiments, a dental adhesive may be applied priorto application of the curable dental restoration material describedherein. Dental adhesives are also typically hardened by curingconcurrently with curing the highly filled dental restorationcomposition. The method of treating an oral surface may compriseproviding a dental article and adhering the dental article to an oral(e.g. tooth) surface.

In other embodiments, the compositions can be cured into dental articlesprior to applying. For example, a dental article such as a crown may bepre-formed from the curable dental composition described herein. Dentalcomposite (e.g. crowns) articles can be made from the curablecomposition described herein by casting the curable composition incontact with a mold and curing the composition. Alternatively, dentalcomposites or articles (e.g. crowns) can be made by first curing thecomposition forming a mill blank and then mechanically milling thecomposition into the desired article.

Another method of treating a tooth surface comprises providing a dentalcomposition as described herein wherein the composition is in the formof a (partially cured) curable, self-supporting, malleable structurehaving a first semi-finished shape; placing the curable dentalcomposition on a tooth surface in the mouth of a subject; customizingthe shape of the curable dental composition; and hardening the curabledental composition. The customization can occur in the patient's mouthor on a model outside the patient mouth such as described in U.S. Pat.No. 7,674,850 (Karim et al.); incorporated herein by reference.

EXAMPLES

Amounts of materials are by weight or weight percent (“wt. %”), unlessdesignated otherwise.

Materials Utilized:

Acetone (EMD Millipore Corporation, Billerica, Mass.)

Aluminum Oxide, powder, </=10 □m avg. particle size (Sigma-Aldrich, St.Louis, Mo.)

3-Amino-3-(2-nitrophenyl)propionic acid, 98% (Alfa Aesar, Ward Hill,Mass.)

Ammonium Chloride (EMD Chemicals, Inc. Gibbstown, N.J.)

BENZOFLEX 9-88, plasticizer (Eastman Chemical Co., Kingsport, Tenn.)

Benzyltributyl ammonium chloride (Sigma-Aldrich, St. Louis, Mo.)

BisGMA: 2,2-Bis[4-hydroxy-3-methacryloyloxy)propoxyphenyl]propane(Sigma-Aldrich, St. Louis, Mo.)

CAB-O-SIL TS720 (Cabot Corporation, Billerica, Mass.)

CDCl₃: Deuterochloroform (Cambridge Isotope Laboratories, Andover,Mass.)

CH₂Cl₂: Dichloromethane (EMD Millipore Corporation, Billerica, Mass.)

CHP: Cumene hydroperoxide, 80% Tech. grade (Alfa Aesar, Heysham,England)

Copper (II) acetate (Sigma-Aldrich, St. Louis, Mo.)

Copper (II) chloride dihydrate (Alfa Aesar, Heysham, England)

Cobalt (II) chloride hexahydrate (Alfa Aesar, Ward Hill, Mass.)

CSA: 10-Camphorsulfonic acid (Aldrich Chemical Co., Milwaukee, Wis.)

1,1-Dimethoxycyclohexane (Sigma-Aldrich, St. Louis, Mo.)

2,2-Dimethoxypropane (Sigma-Aldrich, St. Louis, Mo.)

DMF: Dimethylformamide (EMD Millipore Corporation, Billerica, Mass.)

d₆-DMSO: Dimethylsulfoxide-d₆ (Cambridge Isotope Laboratories, Andover,Mass.)

DVB: Divinylbenzene, 80% technical grade (Sigma-Aldrich, St. Louis, Mo.)

EtOAc: Ethyl acetate (VWR International, Radnor, Pa.)

EtOH: Ethanol (EMD Chemicals, Gibbstown, N.J.)

HDDA: Hexanediol diacrylate, Sartomer SR238B (Warrington, Pa.)

HDK H-2000 Hydrophobic pyrogenic silica (Wacker Silicones. WackerChemical Corp., Adrian, Mich.)

HEMA: 2-Hydroxyethyl methacrylate (Sigma-Aldrich, St. Louis, Mo.)

Hexane (EMD Millipore Corporation, Billerica, Mass.)

Iron (II) chloride tetrahydrate (Alfa Aesar, Ward Hill, Mass.)

L-Ascorbic acid (Alfa Aesar, Ward Hill, Mass.)

MeOH: Methanol (EMD Millipore Corporation, Billerica, Mass.)

MgSO₄: Magnesium sulfate, anhydrous (EMD Chemicals, Inc. Gibbstown,N.J.)

N-methyl morpholine (Aldrich, Milwaukee, Wis.)

2-Picolyl chloride hydrochloride (Sigma-Aldrich, St. Louis, Mo.)

PyBOP: benzotriazol-1-yl-oxytripyrrolidinophosphoniumhexafluorophosphate (Oakwood Chemical, West Columbia, S.C.)

SARTOMER SR203: Tetrahydrofuryl methacrylate (Sartomer, Warrington, Pa.)

SARTOMER SR541: Ethoxylated(6) Bisphenol A dimethacrylate (Sartomer,Warrington, Pa.)

TEGDMA: Tetraethylene glycol dimethacrylate (Sigma-Aldrich, St. Louis,Mo.)

2-Thiopheneethylamine (Aldrich, Milwaukee, Wis.)

2-Thiophenemethylamine (Aldrich, Milwaukee, Wis.)

Triethylamine (EMD Chemicals Inc., Gibbstown, N.J.)

VTBN: 1300X33 VTBNX (Emerald Performance Materials, Akron, Ohio);methacrylate-functional butadiene-acrylonitrile liquid rubber

Z250: Filtek™ Z250 S/T Universal Restorative (3M ESPE)

Test Methods

Barcol Hardness Test Method

“Barcol hardness” of test samples was determined according to thefollowing procedure. Uncured composite samples were placed in a TEFLONmold (4 mm thickness with a 7 mm diameter circular hole in the center)sandwiched between a sheet of polyester (PET) film and a glass slide andirradiated with an OMNICURE LX-400 LED lamp (Lumen Dynamics,Mississauga, Ontario, Canada) at 365 nm for 10 seconds, then allowed tocure in either a 37° C./95% RH chamber, or at ambient temperature, asspecified. Following the specified time lengths, the PET film wasremoved and the hardness of samples at both the top and the bottom ofthe mold were measured using a Barber-Coleman IMPRESSOR (a hand-heldportable hardness tester; MODEL GYZJ 934-1, obtained from Barber-ColemanCompany, Industrial Instruments Division, Lovas Park, Ind.) equippedwith an indenter. The reported “Top Barcol” and “Bottom Barcol” valueswere means from triplicate measurement, with standard deviations listedin parentheses.

Flexural Strength/Flexural Modulus Test Method

Paste samples were extruded into 2 mm×2 mm×25 mm quartz glass molds toform test bars. All test bars were cured for 30 minutes in a 37° C./95%RH chamber, then stored in water at 37° C. for 24 h. Irradiated sampleswere irradiated with an OMNICURE LX400 LED lamp (Lumen Dynamics,Mississauga, Ontario, Canada) at 365 nm for 10 seconds prior to curingas above. Flexural strength and flexural modulus of the bars wasmeasured on an INSTRON tester (INSTRON 4505 or INSTRON 1123, InstronCorp., Canton, Mass.) according to ANSI/ADA (American NationalStandard/American Dental Association) specification No. 27 (1993) at acrosshead speed of 0.75 mm/minute. The results were reported inmegapascals (MPa). The resulting flexural strength and flexural modulusvalues were reported as means from a minimum of five measurements, withstandard deviations listed in parentheses.

Preparative Examples Preparative Example 1 (PE-1): Copper Complex

This copper metal complex designated was prepared according toCiesienski, K. L.; Haas, K. L.; Dickens, M. G.; Tesema, Y. T.; Franz, K.J. “A Photolabile Ligand for Light-Activated Release of Caged Copper” J.Am. Chem. Soc. 2008, vol. 130, pages 12246-12247.

Preparative Example 2 (PE-2): Copper Complex

This copper metal complex was prepared according to Ciesienski, K. L.;Haas, K. L.; Franz, K. J. “Development of Next-generation PhotolabileCages with Improved Copper Binding Properties” Dalton Trans. 2010, vol.39, pages 9538-9546.

Preparative Example 3 (PE-3): Copper Complex

This copper metal complex was prepared according to Ciesienski, K. L.;Haas, K. L.; Franz, K. J. “Development of Next-generation PhotolabileCages with Improved Copper Binding Properties” Dalton Trans. 2010, vol.39, pages 9538-9546.

Preparative Example 4 (PE-4): Copper Complex

A slurry of 3-amino-3-(2-nitrophenyl)propionic acid (30.0 mmol, 6.31 g)and N-methyl morpholine (60.0 mmol, 6.07 g) in DMF (100 mL) was heatedat 70° C. with a heating mantle under nitrogen atmosphere. A solution of2-picolyl chloride hydrochloride (30.0 mmol, 5.34 g) in DMF (20 mL) wasadded via pipette. The resultant solution was heated 70° C. overnight.Following addition of H₂O (200 mL), the reaction mixture was extractedwith EtOAc (4×75 mL). The combined organic layers were then extractedwith 1N aq. NaOH (2×75 mL). The combined 1N aq. NaOH layers wereacidified to pH ˜3 via addition of conc. HCl, then extracted with EtOAc(3×75 mL). These combined EtOAc layers were washed with H₂O (2×) andsat. aq. NaCl (lx), dried over MgSO₄, filtered, and concentrated to alight tan oil under reduced pressure. This material foams under vacuumto afford the desired amide product (5.86 g, 62% yield), which wasrevealed by ¹H NMR to be sufficiently clean to carry forward withoutadditional purification. To a solution of this amide (18.6 mmol, 5.86g), 2-thiophenemethylamine (18.6 mmol, 2.10 g), and N-methyl morpholine(18.6 mmol, 1.88 g) in CH₂Cl₂ (150 mL) was added PyBOP (18.6 mmol, 9.67g). The resultant reaction mixture was heated at reflux with a heatingmantle while stirring under nitrogen atmosphere overnight. The reactionmixture was then washed with H₂O (2×) and sat. aq. NaCl (lx), dried overMgSO₄, filtered, and concentrated to an orange oil. This crude reactionproduct was purified via silica gel flash chromatography (ramp eluentfrom 1:1 hexane/EtOAc to 2:3 hexane/EtOAc) to afford a yellow solid.This solid was further purified via trituration with a hexane/EtOAcmixture to afford the ligand as a white solid (3.51 g, 46% yield). ¹HNMR (CDCl₃, 500 MHz) shows this to be clean material and consistent withthe reported structure. A portion of this ligand (1.7 mmol, 0.70 g) wasadded to EtOH (40 mL). Copper (II) chloride dihydrate (1.7 mmol, 0.29 g)was then added, and the resultant mixture rapidly becomes a homogeneousblue solution. The solution was heated at reflux with stirringovernight. The EtOH was then removed under reduced pressure, and MeOHwas added to the residue. The mixture was filtered through a short plugof aluminum oxide. The blue colored filtrate was concentrated and driedunder vacuum to afford the desired copper metal complex (PE-4) as agreenish-brown solid (0.91 g).

Preparative Example 5 (PE-5): Copper Complex

A slurry of 3-amino-3-(2-nitrophenyl)propionic acid (20.0 mmol, 4.20 g)and N-methyl morpholine (40.0 mmol, 4.05 g) in DMF (100 mL) was heated70° C. with a heating mantle under nitrogen atmosphere. A solution of2-picolyl chloride hydrochloride (20.0 mmol, 3.56 g) in DMF (20 mL) wasadded via pipette. The resultant solution was heated at 70° C.overnight. Following addition of H₂O (200 mL), the reaction mixture wasextracted with EtOAc (4×75 mL). The combined organic layers were thenextracted with 1N aq. NaOH (2×75 mL). The combined 1N aq. NaOH layerswere acidified to pH ˜3 via addition of conc. HCl, then extracted withEtOAc (3×75 mL). These combined EtOAc layers were washed with H₂O (2×)and sat. aq. NaCl (lx), dried over MgSO₄, filtered, and concentratedunder reduced pressure to provide a light tan oil. This material foamsunder vacuum to afford the desired amide product (3.79 g, 60% yield),which was revealed by ¹H NMR to be sufficiently clean to carry forwardwithout additional purification. To a solution of this amide (7.29 mmol,2.30 g), 2-thiopheneethylamine (7.29 mmol, 0.93 g), and N-methylmorpholine (7.29 mmol, 0.74 g) in CH₂Cl₂ (80 mL) was added PyBOP (7.29mmol, 3.79 g). The resultant reaction mixture was heated at reflux witha heating mantle while stirring under nitrogen atmosphere overnight. Thereaction mixture was then washed with H₂O (2×) and sat. aq. NaCl (1×),dried over MgSO₄, filtered, and concentrated to an orange oil. Thiscrude reaction product was purified via silica gel flash chromatography(1:1 hexane/EtOAc eluent) to afford a yellow solid. This solid wasfurther purified via trituration with a hexane/EtOAc mixture to affordthe ligand as a white solid (0.85 g, 28% yield). ¹H 1 NMR (CDCl₃, 500MHz) shows this to be clean material and consistent with the reportedstructure. A portion of this ligand (1.0 mmol, 0.42 g) was added to EtOH(40 mL). Copper (II) chloride dihydrate (1.0 mmol, 0.17 g) was thenadded, and the resultant mixture rapidly becomes a homogeneous bluesolution. The solution was heated at reflux with stirring overnight. TheEtOH was then removed under reduced pressure, and MeOH was added to theresidue. The mixture was filtered through a short plug of aluminumoxide. The blue colored filtrate was concentrated and dried under vacuumto afford the desired copper metal complex (PE-5) as a greenish-brownsolid (0.54 g).

Preparative Example 6 (PE-6): Iron Complex

The ligand for this complex was prepared as reported in Ciesienski, K.L.; Haas, K. L.; Dickens, M. G.; Tesema, Y. T.; Franz, K. J. “APhotolabile Ligand for Light-Activated Release of Caged Copper” J. Am.Chem. Soc. 2008, vol. 130, pages 12246-12247. This ligand (1.00 g, 2.47mmol) was added to 100 mL EtOH and heated at gentle reflux. Iron (II)chloride tetrahydrate (0.49 g, 2.47 mmol), was added, resulting in animmediate formation of a dark red solution. After heating overnight, theEtOH was removed under reduced pressure, and the resultant red solid wasdissolved in MeOH. The mixture was filtered through a plug of alumina toremove residual solids. The filtrate was concentrated and dried undervacuum, providing the iron complex (PE-6) as a red-brown solid (1.10 g).

Preparative Example 7 (PE-7): Iron Complex

The ligand for this complex was prepared according to Ciesienski, K. L.;Haas, K. L.; Franz, K. J. “Development of Next-generation PhotolabileCages with Improved Copper Binding Properties” Dalton Trans. 2010, vol.39, pages 9538-9546. This ligand (0.95 g, 2.33 mmol) was dissolved in100 ml EtOH. Iron (II) chloride tetrahydrate (0.46 g, 2.33 mmol) wasadded, resulting in the formation of a red solution which was heated atreflux overnight. The EtOH was removed under reduced pressure, and theresidue was filtered through a plug of aluminum oxide, eluting withmethanol. The filtrate was concentrated and dried under vacuum to affordthe iron complex (PE-7) as a red-brown solid (0.92 g).

Preparative Example 8 (PE-8): Cobalt Complex

The ligand for this complex was prepared according to Ciesienski, K. L.;Haas, K. L.; Dickens, M. G.; Tesema, Y. T.; Franz, K. J. “A PhotolabileLigand for Light-Activated Release of Caged Copper” J. Am. Chem. Soc.2008, vol. 130, pages 12246-12247. This ligand (1.24 g, 3.06 mmol) wasdissolved in 75 ml EtOH. Cobalt (II) chloride hexahydrate (0.73 g, 3.06mmol) was added, resulting in the formation of a bright blue slurrywhich was heated at reflux overnight. The EtOH was removed under reducedpressure, and the residue was filtered through a plug of aluminum oxide,eluting with methanol. The filtrate was concentrated and dried undervacuum to afford the cobalt complex (PE-8) as a blue solid (0.72 g).

Preparative Example 9 (PE-9): Synthesis of Cyc-AA

To a suspension of L-ascorbic acid (10.0 g, 56.8 mmol) in 100 mL acetonewas added 1,1-dimethoxycyclohexane (13.9 g, 96.6 mmol) and10-camphorsulfonic acid (0.66 g, 2.84 mmol). The resultant mixture wasallowed to stir at room temperature under nitrogen atmosphere, andslowly became a clear, nearly colorless solution. After 48 hours, thesolution had become pale yellow in color. Approximately 0.4 g oftriethylamine was added, which resulted in the solution becoming nearlycolorless again. The solvents were removed under reduced pressure toafford a white solid which was triturated with a 9:1 hexane/EtOAcmixture. The precipitate was collected via filtration and dried undervacuum to afford the product as a white solid (13.0 g, 89% yield). ¹HNMR signals were consistent with the desired product.

Preparative Example 10 (PE-10): Synthesis of5,6-O-Isopropylidene-L-Ascorbic Acid (p-AA)

This material was prepared according to literature precedence (Bioorg.Med. Chem. 2003, vol. 11, 827). To a suspension of L-ascorbic acid (20.0g, 114 mmol) in acetone (200 mL) was added 2,2-dimethoxypropane (20.4 g,196 mmol) and 10-camphorsulfonic acid (1.32 g, 5.68 mmol). The resultantmixture was allowed to stir overnight at room temperature. To theresultant slurry was added approximately 0.6 g triethylamine. A portionof hexane was added to the mixture, and the white precipitate wascollected via vacuum filtration, washing with additional hexane. Thematerial was dried under vacuum to afford the desired product (21.0 g,86% yield). ¹H NMR (d₆-DMSO, 500 MHz) was consistent with the desiredproduct.

Examples of Two-Part Methacrylate-Based Formulations

Examples of two-part formulations were provided that included apolymerizable methacrylate-based monomer.

Example 1 (EX-1): Two-Part Formulation Using the PE-1 Copper Complex

A representative two-part dental composite formulation was prepared asfollows. A “Mixture-A” paste included a 1:1 mixture of BisGMA and TEGDMAas polymerizable methacrylate-based monomers,5,6-O-isopropylidene-L-ascorbic acid (p-AA), HDK H-2000 fumed silica asa flow agent, and Z250 as filler material, according to the amountslisted in Table 1. A “Mixture-B” paste included a 1:1 mixture of BisGMAand TEGDMA, a 2 wt. % solution of PE-1 Copper Complex dissolved in 1:1BisGMA/TEGDMA, cumene hydroperoxide (CHP), HDK H-2000 fumed silica, andZ250 filler, according to the amounts listed in Table 1.

TABLE 1 Material Wt. % mass (g) Mixture-A BisGMA 19.5 1.95 TEGDMA 19.51.95 — — — p-AA 0.5 0.05 HDK H-2000 2.0 0.20 Z250 filler 58.5 5.85 Total100.0 10.00 Mixture-B BisGMA 18.95 1.90 TEGDMA 18.95 1.90 Cu cage soln*0.10 0.01 CHP 1.00 0.10 HDK H-2000 2.00 0.20 Z250 filler 59.00 5.90Total 100.00 10.00 *The “Cu cage soln” of EX-1 was prepared as a 2 wt. %solution of PE-1 Cu complex in 1:1 BisGMA/TEGDMA; thus the Mixture-Bpaste was 0.002 wt. % PE-1 Cu complex

To perform curing experiments with the EX-1 two-part formulation, 60 mgportions of each of the Mixture-A and Mixture-B parts of EX-1 wereweighed out onto a mixing pad and hand mixed together for 20 seconds. Attime=30 seconds, the mixture was irradiated with an LX-400 LED lamp(Lumen Dynamics, Mississauga, Ontario, Canada) held 2 cm from themixture for the specified time at the specified wavelength, assummarized in Table 2. A dental probe was then used to evaluate the cureof the material. Working time was defined as the elapsed time until thefirst solid chunk of cured material could be detected, and full cure wasdefined as the elapsed time until the entire sample had cured to asolid. Results were as summarized in Table 2.

TABLE 2* 365 nm 385 nm 400 nm Irradiation full full work full time, worktime, cure, work time, cure, time, cure, seconds minutes minutes minutesminutes minutes minutes 0 5.25 6.50 5.25 6.50 5.25 6.50 5.0 4.00 5.504.25 5.50 4.75 5.75 7.5 2.25 4.25 3.25 4.75 4.50 5.25 10 1.00 3.75 1.504.25 4.25 5.00 *Work time = time until the first amount of curedmaterial could be detected; Full cure = time until the entire pastesample became hardened.

Example 2 (EX-2): Two-Part Formulation Using the PE-4 Copper Complex

A two-part formulation was prepared according to the method described inExample 1, except that the PE-4 Copper complex material was used inplace of the PE-1 Copper complex material, and using the amounts assummarized in Table 3.

TABLE 3 Material Wt. % mass (g) Mixture-A BisGMA 19.5 1.95 TEGDMA 19.51.95 — — — p-AA 0.5 0.05 HDK H-2000 2.0 0.20 Z250 filler 58.5 5.85 Total100.0 10.00 Mixture-B BisGMA 18.95 1.90 TEGDMA 18.95 1.90 Cu cage soln*0.10 0.01 CHP 1.00 0.10 HDK H-2000 2.00 0.20 Z250 filler 59.00 5.90Total 100.00 10.00 *The “Cu cage soln” of EX-2 was prepared as a 2 wt. %solution of PE-4 Cu complex in 1:1 BisGMA/TEGDMA; thus the Mixture-Bpaste was 0.002 wt. % PE-4 Cu complex

To perform curing experiments with the EX-2 two-part formulation, 60 mgportions of each of the Mixture-A and Mixture-B parts of EX-2 wereweighed out onto a mixing pad and hand mixed together for 20 seconds. Attime=30 seconds, the mixture was irradiated with an LX-400 LED lamp(Lumen Dynamics, Mississauga, Ontario, Canada) held 2 cm from themixture for the specified time at the specified wavelength (365 nm, 385nm, or 400 nm), as summarized in Table 4. A dental probe was then usedto evaluate the cure of the material. Working time was defined as theelapsed time until the first solid chunk of cured material could bedetected, and full cure was defined as the elapsed time until the entiresample had cured to a solid. Results were as summarized in Table 4.

TABLE 4* 365 nm 385 nm 400 nm Irradiation full full work full time, worktime, cure, work time, cure, time, cure, seconds minutes minutes minutesminutes minutes minutes 0 6.50 7.75 6.50 7.75 6.50 7.75 5.0 5.25 7.005.50 7.00 6.25 7.50 7.5 3.00 4.75 3.75 5.50 6.00 7.00 10 1.00 3.25 2.254.00 5.00 6.50 *Work time = time until the first amount of curedmaterial could be detected; Full cure = time until the entire pastesample became hardened.

Example 3 (EX-3): Two-Part Formulation Using the PE-3 Copper Complex

A two-part formulation was prepared according to the method described inEX-1, except that the PE-3 Copper complex material was used in place ofthe PE-1 Copper complex material, using the amounts as summarized inTable 5.

TABLE 5 Material Wt. % mass (g) Mixture-A BisGMA 19.5 1.95 TEGDMA 19.51.95 — — — p-AA 0.5 0.05 HDK H-2000 2.0 0.20 Z250 filler 58.5 5.85 Total100.0 10.00 Mixture-B BisGMA 18.95 1.90 TEGDMA 18.95 1.90 Cu cage soln*0.10 0.01 CHP 1.00 0.10 HDK H-2000 2.00 0.20 Z250 filler 59.00 5.90Total 100.00 10.00 *The “Cu cage soln” of EX-3 was prepared as a 2 wt. %solution of PE-3 Copper complex in 1:1 BisGMA/TEGDMA; thus the Mixture-Bpaste was 0.002 wt. % PE-3 Copper complex

To perform curing experiments with the EX-3 two-part formulation, 60 mgportions of each of the Mixture-A and Mixture-B parts of EX-3 wereweighed out onto a mixing pad and hand mixed together for 20 seconds. Attime=30 seconds, the mixture was irradiated with an LX-400 LED lamp(Lumen Dynamics, Mississauga, Ontario, Canada) held 2 cm from themixture for the specified time at the specified wavelength (365 nm, 385nm, or 400 nm), as summarized in Table 6. A dental probe was then usedto evaluate the cure of the material. Working time was defined as theelapsed time until the first solid chunk of cured material can bedetected, and full cure was defined as the elapsed time until the entiresample had cured to a solid. Results were as summarized in Table 6.

TABLE 6* 365 nm 385 nm 400 nm Irradiation full full work full time, worktime, cure, work time, cure, time, cure, seconds minutes minutes minutesminutes minutes minutes 0 7.50 12.00 7.50 12.00 7.50 12.00 5.0 1.50 3.252.75 3.75 4.25 5.50 7.5 0.75 1.50 1.25 2.50 3.50 4.50 10 <0.75 1.00 0.751.50 2.75 3.50 *Work time = time until the first amount of curedmaterial could be detected; Full cure = time until the entire pastesample became hardened.

Example 4 (EX-4): Two-Part Formulation Using the PE-6 Iron Complex

For experiments containing this PE-6 iron complex, a “Mixture-A” pasteincluded a 1:1 mixture of BisGMA and TEGDMA,5,6-O-isopropylidene-L-ascorbic acid (p-AA), cumene hydroperoxide (CHP),HDK H-2000 fumed silica, and Z250 filler in the amounts listed in Table7. “Mixture-B” paste included a 1:1 mixture of BisGMA and TEGDMA aspolymerizable methacrylate-based monomers, a 2 wt. % solution of thePE-6 iron complex dissolved in 1:1 BisGMA/TEGDMA, a 20 wt. % solution ofammonium chloride dissolved in 2-hydroxyethyl methacrylate (HEMA), HDKH-2000 fumed silica as a flow agent, and Z250 as filler material in theamounts listed in Table 7.

TABLE 7 Material Wt. % mass (g) Mixture-A BisGMA 20.00 2.00 TEGDMA 20.002.00 p-AA 0.50 0.05 CHP 2.00 0.20 HDK H-2000 1.00 0.10 Z250 filler 56.505.65 Total 100.00 10.00 Mixture-B BisGMA 18.00 1.80 TEGDMA 18.00 1.80 Fecage soln* 2.00 0.20 Am. Cl soln** 5.00 0.50 HDK H-2000 1.00 0.10 Z250filler 56.00 5.60 Total 100.00 10.00 *The “Fe cage soln” of EX-4 wasprepared as a 2 wt. % solution of PE-6 iron complex in 1:1BisGMA/TEGDMA; thus the Mixture-B paste was 0.04 wt. % PE-6 ironcomplex. **The “Am. Cl. soln” was 20 wt. % benzyltributyl ammoniumchloride in HEMA.

To perform curing experiments with the EX-4 two-part formulation, 60 mgportions of each of the Mixture-A and Mixture-B parts of EX-4 were thenweighed out onto a mixing pad and hand mixed together for 20 seconds. Attime=30 seconds, the mixture was then irradiated either with an LX-400LED lamp (Lumen Dynamics, Mississauga, Ontario, Canada) held 2 cm fromthe mixture for the specified time at the specified wavelength (365 nm,385 nm, or 400 nm), or in the case of 450 nm irradiation, with an ELIPARS10 LED Curing Light (3M ESPE, St. Paul, Minn.) held <1 cm from thesample. The sample was then placed in a 37° C. chamber. A dental probewas then used to evaluate the cure of the material. Working time wasdefined as the elapsed time until the first solid chunk of curedmaterial can be detected, and full cure was defined as the elapsed timeuntil the entire sample had cured to a solid.

TABLE 8* Irradiation 365 nm 385 nm 400 nm 450 nm time, full cure, fullcure, full cure, full cure, seconds minutes minutes minutes minutes 010.0 10.0 10.0 10.0 2.0 3.5 4.0 5.5 6.0 4.0 2.5 3.0 4.5 5.5 6.0 1.0 2.03.5 5.0 *Full cure = time until the entire paste sample became hardened.

Comparative Example 1 (CE-1): Two-Part Formulation Using Cu(OAc)₂

A comparative example of a two-part formulation was prepared accordingto the method used for EX-1, except that copper (II) acetate was thecopper source, with amounts as summarized in Table 9.

TABLE 9 Mixture-A Mixture-B mass mass Material Wt. % (g) Material Wt. %(g) BisGMA 19.5 11.7 BisGMA 18.95 3.79 TEGDMA 19.5 11.7 TEGDMA 18.953.79 — — — Cu(OAc)₂ soln* 0.60 0.12 p-AA 0.5 0.3 CHP 1.00 0.20 HDKH-2000 2.0 1.2 HDK H-2000 2.00 0.40 Z250 filler 58.5 35.1 Z250 filler59.00 11.70 Total 100.0 60.0 Total 100.00 20.00 *The “Cu(OAc)₂ soln” ofCE-1 was prepared as a 1.7 wt. % solution of Cu(OAc)₂ in 1:1BisGMA/TEGDMA; thus the Mixture-B paste was 0.0102 wt. % Cu(OAc)₂

Barcol hardness values of test samples from CE-1, EX-1, and EX-3 weredetermined according to the “Barcol Hardness Test Method” describedabove, using a 37° C./95% RH chamber for treatment during the curingtime. The “Top Barcol” and “Bottom Barcol” values reported in Table 10were means from triplicate measurement, with standard deviations listedin parentheses.

TABLE 10 Two-part Irradiation Curing Top Bottom formulation (10 secondsat 365 nm) time Barcol Barcol CE-1 No 15 min 30.0 (0.8) 29.3 (0.5) 30min 47.0 (1.4) 50.0 (1.6) 45 min 57.7 (0.5) 59.3 (0.9) 60 min 63.3 (1.3)61.7 (0.5) EX-1 No 15 min 28.0 (0.0) 30.0 (1.6) 30 min 42.0 (0.0) 42.7(0.5) 45 min 48.0 (0.8) 49.3 (0.5) 60 min 53.3 (0.9) 55.3 (0.9) Yes 15min 40.0 (1.6) 41.7 (0.5) 30 min 49.3 (0.9) 50.7 (0.9) 45 min 54.7 (0.9)55.0 (0.8) 60 min 57.3 (0.9) 57.3 (0.5) EX-3 No 10 min 0 0 20 min 0 0 30min  5.3 (0.6)  5.3 (0.6) 40 min  9.7 (0.6)  9.3 (0.6) 60 min 22.7 (1.2)23.0 (1.0) 90 min 48.0 (1.0) 47.3 (1.2) Yes 10 min 0 0 20 min 11.3 (1.2)10.3 (1.5) 30 min 22.7 (0.6) 23.0 (1.0) 40 min 31.0 (1.0) 33.7 (1.2) 60min 40.0 (1.0) 39.7 (0.6) 90 min 55.0 (1.0) 56.3 (0.6)

Flexural strength and flexural modulus values of test samples from CE-1,EX-1, and EX-3 were determined according to the “FlexuralStrength/Flexural Modulus Test Method” described above. The resultingflexural strength and flexural modulus values (in MPa) listed in Table11 were means from a minimum of five measurements, with standarddeviations (in MPa) listed in parentheses.

TABLE 11 Flexural Two-part Irradiation Flexural strength, modulus,formulation (10 seconds at 365 nm) MPa MPa CE-1 No 98.6 (11.7) 6.11(0.4) EX-1 No 83.9 (12.2) 5.36 (0.4) Yes 108.0 (12.0)  5.40 (0.4) EX-3No 63.5 (13.9) 3.60 (0.4) Yes 88.6 (14.8) 4.62 (0.8)

Examples of Two-Part Acrylate-Based Formulations

Examples of two-part formulations were provided that included apolymerizable acrylate-based monomer.

Example 5 (EX-5): Two-Part Formulation Using the PE-1 Copper Complex

A representative two-part formulation was prepared as follows. A“Mixture-A” paste included SARTOMER SR238B (hexanediol diacrylate, HDDA)as a polymerizable acrylate-based monomer,5,6-O-isopropylidene-L-ascorbic acid (p-AA), HDK H-2000 fumed silica asa flow agent, and Z250 as filler material in the amounts listed in Table13. A “Mixture-B” paste included SARTOMER SR238B (hexanediol diacrylate,HDDA), a 2 wt. % solution of the PE-1 copper (II) cage complex dissolvedin 1:1 BisGMA/TEGDMA, cumene hydroperoxide (CHP), HDK H-2000 fumedsilica, and Z250 filler in the amounts listed in Table 12.

TABLE 12 Mixture-A Mixture-B mass mass Material Wt. % (g) Material Wt. %(g) HDDA 37.5 3.75 HDDA 36.50 7.30 p-AA 0.5 0.05 Cu cage soln* 0.15 0.03— — — CHP 1.00 0.20 HDK H-2000 4.0 0.40 HDK H-2000 4.00 0.80 Z250 filler58.0 5.80 Z250 filler 58.35 11.67 Total 100.0 10.00 Total 100.00 20.00*The “Cu cage soln” of Example 5 was prepared as a 2 wt. % solution ofPE-1 Cu complex in 1:1 BisGMA/TEGDMA; thus the Mixture-B paste was 0.003wt. % PE-1 Cu complex.

To perform curing experiments with the EX-5 two-part formulation, 60 mgportions of each of the Mixture-A and Mixture-B parts of EX-5 wereweighed out onto a mixing pad and hand mixed together for 20 seconds. Attime=30 seconds, the mixture was irradiated either with an LX-400 LEDlamp (Lumen Dynamics, Mississauga, Ontario, Canada) held 2 cm from themixture for the specified time at the specified wavelength, assummarized in Table 13, or in the case of 450 nm with an ELIPAR S10 LEDCuring Light (3M ESPE, St. Paul, Minn.) held <1 cm from the mixture. Adental probe was then used to evaluate the cure of the material. Workingtime was defined as the elapsed time until the first solid chunk ofcured material could be detected, and full cure was defined as theelapsed time until the entire sample had cured to a solid. Results wereas summarized in Table 13.

TABLE 13* 365 nm 385 nm 400 nm 450 nm Irradiation work full work fullwork full work full time, time, cure, time, cure, time, cure, time,cure, seconds minutes minutes minutes minutes minutes minutes minutesminutes 0 5.50 8.00 5.50 8.00 5.50 8.00 5.50 8.00 5.0 3.50 4.50 4.506.00 5.25 7.00 5.00 6.00 10.0 2.00 3.00 4.00 5.75 4.50 6.00 4.00 4.5015.0 <0.75 0.75 2.25 4.00 4.00 5.75 3.50 4.00 *Work time = time untilthe first amount of cured material could be detected; Full cure = timeuntil the entire paste sample became hardened.

Comparative Example 2 (CE-2): Two-Part Formulation Using Cu(OAc)₂

A comparative example of a two-part formulation was prepared accordingto the method used for EX-5, except that copper (II) acetate was thecopper source, with amounts as summarized in Table 14.

TABLE 14 Mixture-A Mixture-B mass mass Material Wt. % (g) Material Wt. %(g) HDDA 37.5 3.75 HDDA 36.50 7.30 p-AA 0.5 0.05 Cu(OAc)₂ soln* 0.150.03 — — — CHP 1.00 0.20 HDK H-2000 4.0 0.40 HDK H-2000 4.00 0.80 Z250filler 58.0 5.80 Z250 filler 58.35 11.67 Total 100.0 10.00 Total 100.0020.00 *The “Cu(OAc)₂ soln” of CE-2 was prepared as a 1.7 wt. % solutionof Cu(OAc)₂ in 1:1 BisGMA/TEGDMA; thus the Mixture-B paste was 0.0026wt. % Cu(OAc)₂

Barcol hardness values of test samples from CE-2 and EX-5 weredetermined according to the “Barcol Hardness Test Method” describedabove, using ambient temperature during the curing time. The “TopBarcol” and “Bottom Barcol” values reported in Table 15 were means fromtriplicate measurement, with standard deviations listed in parentheses.

TABLE 15 Two-part Irradiation Curing Top Bottom formulation (10 secondsat 365 nm) time Barcol Barcol CE-2 No  5 min 0 0 10 min 47.3 (0.3) 47.0(1.0) 15 min 65.0 (0.0) 65.0 (1.0) 20 min 65.0 (1.0) 65.7 (0.6) EX-5 No 5 min 0 0 10 min 53.3 (1.2) 53.0 (1.0) 15 min 66.3 (0.6) 66.0 (0.0) 20min 65.7 (0.6) 66.7 (0.6) Yes  5 min 37.7 (0.6) 37.0 (1.0) 10 min 65.0(1.0) 64.3 (0.6) 15 min 66.3 (0.6) 67.0 (0.0) 20 min 66.3 (1.2) 67.0(1.0)Curing Experiments with Vinyl-Based Formulations

An example of a one-part formulation was provided that included apolymerizable vinyl-based monomer.

Example 6 (EX-6): One-Part Formulation Using the PE-1 Copper Complex

A representative formulation was prepared which included divinylbenzene(DVB) as the polymerizable vinyl-based monomer, ethyl acetate (EtOAc),cyclohexyl ketal-protected ascorbic acid (cyc-AA), cumene hydroperoxide(CHP), and a 1.7 wt. % solution of the PE-1 copper complex in ethylacetate, according to the amounts in Table 16.

TABLE 16 Material Wt. % mass (g) DVB 49.0 44.10 EtOAc 49.0 44.10 cyc-AA0.5 0.45 CHP 1.0 0.90 Cu cage soln* 0.5 0.45 Total 100.0 90.00 *The “Cucage soln” of Example 6 was prepared as a 1.7 wt. % solution of PE-1 Cucomplex in 1:1 BisGMA/TEGDMA; thus the resin was 0.0085 wt. % PE-1 Cucomplex.

To perform curing experiments, nitrogen was bubbled through the EX-6formulation for several minutes, then 6.0 gram samples were placed in 20mL glass vials which were flushed with nitrogen, and then capped with ascrew-top cap. The samples were then irradiated through the bottom ofthe vial using an LX400 LED lamp (Lumen Dynamics, Mississauga, Ontario,Canada) at 365 nm for 5×1 minute. Afterwards, at the times specified inTable 17, any polymerized material was collected by vacuum filtration.The collected precipitate was then ground to a fine powder, stirred withethyl acetate for 30 min, collected again via vacuum filtration, driedunder vacuum, and weighed. The amounts of polymerized material collectedand corresponding percent conversion values were as summarized in Table17.

TABLE 17 UV irradiation No UV irradiation Time, poly(DVB), poly(DVB),hours grams % conversion grams % conversion 0 0 0 0 0 8 0.74 25.2 0 0 161.24 42.2 0 0 24 1.58 53.7 0.30 10.2 40 1.92 65.3 1.10 37.4 48 1.96 66.71.40 47.6 64 2.16 73.5 1.71 58.2 70 2.21 75.2 1.81 61.6Additional Curing Experiments with Methacrylate-Based Formulation

Example 7 (EX-7): Two-Part Formulation Using the PE-1 Copper Complex

A representative two-part formulation was prepared as shown below. A“Mixture-A” paste included SARTOMER SR203 (THF methacrylate) and asolution of the PE-1 copper complex dissolved in a 1:1 mixture ofBisGMA/TEGDMA, in amounts according to Table 18. A “Mixture-B” pasteincluded BENZOFLEX 9-88, CAB-O-SIL TS720 fumed silica,isopropylidene-protected ascorbic acid (p-AA), and cumene hydroperoxide(CHP), in amounts according to Table 18.

TABLE 18 Mixture-A Mixture-B mass, Wt. mass, Material Wt. % gramsMaterial % grams SR203 98.8 19.75 BENZOFLEX 9-88 89.0 4.45 Cu cage soln*1.2 0.25 CAB-O-SIL TS720 1.8 0.09 — — — p-AA 7.4 0.37 — — — CHP 1.8 0.09Total 100.0 20.00 Total 100.0 5.00 *The “Cu cage soln” of EX-7 wasprepared as a 2 wt. % solution of PE-1 Cu complex in 1:1 BisGMA/TEGDMA;thus the Mixture-A resin was 0.024 wt. % PE-1 Cu complex

To perform curing experiments with the EX-7 two-part formulation, 0.25mL of Mixture-B was added to 2.00 g of Mixture-A in an 8-mL glass vialand shaking briefly to mix. The vial was then irradiated with an LX-400LED lamp (Lumen Dynamics, Mississauga, Ontario, Canada) held within 1 cmof the glass vial for the specified time at the specified wavelength.Working time was defined as the point at which the material was fullysolidified and was no longer able to flow. Irradiation and working timeswere as summarized in Table 19.

TABLE 19 Irradiation at 365 nm, Work time, seconds minutes 0 9.0 30 6.060 4.5

Example 8 (EX-8): Two-Part Formulation Using the PE-3 Copper Complex

A representative two-part formulation was prepared as shown below. A“Mixture-A” paste included SARTOMER SR203 (THF methacrylate) and asolution of the PE-3 copper complex dissolved in a 1:1 mixture ofBisGMA/TEGDMA in amounts according to Table 20. A “Mixture-B” pasteincluded BENZOFLEX 9-88, CAB-O-SIL TS720 fumed silica,isopropylidene-protected ascorbic acid (p-AA), and cumene hydroperoxide(CHP) in amounts according to Table 20.

TABLE 20 Mixture-A Mixture-B mass, Wt. mass, Material Wt. % gramsMaterial % grams SR203 98.8 19.75 BENZOFLEX 9-88 89.0 4.45 Cu cage soln*1.2 0.25 Cab-o-Sil TS720 1.8 0.09 — — — p-AA 7.4 0.37 — — — CHP 1.8 0.09Total 100.0 20.00 Total 100.0 5.00 *The “Cu cage soln” of EX-8 wasprepared as a 2 wt. % solution of PE-3 Cu complex in 1:1 BisGMA/TEGDMA;thus the Mixture-A resin was 0.024 wt. % PE-3 Cu complex

To perform curing experiments with the EX-8 two-part formulation, 0.25mL of Mixture-B was added to 2.00 g of Mixture-A in an 8-mL glass vialand shaking briefly to mix. The vial was then irradiated with an LX-400LED lamp held within 1 cm of the glass vial for the specified time atthe specified wavelength. Working time was defined as the point at whichthe material was fully solidified and no longer able to flow.Irradiation and working times were as summarized in Table 21.

TABLE 21 Irradiation at 365 nm, Work time, seconds minutes 0 6.50 155.75 30 4.75 60 4.25

Example 9 (EX-9): Two-Part Formulation Using the PE-1 Copper Complex

A representative two-part structural adhesive formulation was preparedas shown below. A “Mixture-A” paste included 15 wt. % VTBN in SARTOMERSR203, SARTOMER SR541, CAB-O-SIL TS720 fumed silica, and the PE-1 coppercomplex dissolved in a 1:1 mixture of BisGMA/TEGDMA, in the amountslisted in Table 22. 5-mil spacer beads (E-Spheres SL300 CeramicMicrospheres obtained from Envirospheres PTY Ltd., Lindfield NSW,Australia) were also added to Mixture-A in an amount of 0.5 parts byweight relative to a total 100 parts by weight of the other Mixture-Acomponents. A “Mixture-B” paste included isopropylidene-protectedascorbic acid (p-AA), BENZOFLEX 9-88, cumene hydroperoxide (CHP), andCAB-O-SIL TS720 fumed silica, in the amounts listed in Table 22.

TABLE 22 Mixture-A Mixture-B Wt. mass, Wt. mass, Material % gramsMaterial % grams 15 wt. % VTBN 79.6 7.96 BENZOFLEX 89.0 4.45 in SR2039-88 SR541 14.7 1.47 CAB-O-SIL 1.8 0.09 TS720 Cu cage solution* 0.170.02 p-AA 7.4 0.37 CAB-O-SIL 5.50 0.55 CHP 1.8 0.09 TS720 Total 100.010.00 Total 100.0 5.00 *The “Cu cage solution” was prepared as a 2 wt. %solution of PE-1 Cu complex in 1:1 BisGMA/TEGDMA; thus the Mixture-Apaste was 0.0034 wt. % PE-1 Cu complex.

Comparative Example 3 (CE-3): Two-Part Formulation Using Cu(OAc)₂

A comparative example of a two-part formulation was prepared accordingto the method used for EX-9, except that copper (II) acetate was thecopper source, with amounts as summarized in Table 23.

TABLE 23 Mixture-A Mixture-B mass, mass, Material Wt. % grams MaterialWt. % grams 15 wt. % VTBN 79.6 7.96 BENZOFLEX 89.0 4.45 in SR203 9-88SR541 14.7 1.47 CAB-O-SIL 1.8 0.09 TS720 Cu(OAc)₂ 0.17 0.02 p-AA 7.40.37 solution* CAB-O-SIL 5.50 0.55 CHP 1.8 0.09 TS720 Total 100.0 10.00Total 100.0 5.00 *The “Cu(OAc)₂ solution” was prepared as a 2 wt. %solution of Cu(OAc)₂ in 1:1 BisGMA/TEGDMA; thus the Mixture-A paste was0.0034 wt. % Cu(OAc)₂.

For curing experiments using either CE-3 or EX-9, an 8:1 ratio of thecorresponding Mixture-A paste and Mixture-B paste was weighed out andhand mixed, then spread onto hand-roughened aluminum shims (scrubbedwith 3M SCOTCH-BRITE GENERAL PURPOSE HAND PADS #7447, obtained from 3MCo., St. Paul, Minn.). Irradiated samples (i.e. samples utilizing theformulations with the copper cage complex; the control sample CE-3 wasnot irradiated) were passed through a fusion processor (2 J/cm² D-bulb,obtained from Heraeus Noblelight America, Gaithersburg, Md.) and clampedshut with 0.5 inch (˜1.3 cm) overlap. Samples containing the copper (II)acetate were not irradiated prior to clamping shut with 0.5 inch (˜1.3cm) overlap. All samples were allowed to sit at room temperature for 24hours prior to overlap shear testing. A dynamic overlap shear test wasperformed at ambient temperature using an MTS SINTECH TENSILE TESTER(obtained from MTS Systems, Eden Prairie, Minn.). Test specimens wereloaded into the grips and the crosshead was operated at 0.1 inch (˜2.5mm) per minute, loading the specimen to failure. Samples were run intriplicate and results were reported as the averages. Stress at breakwas recorded in units of pounds per square inch (“psi”), which was alsoconverted to units of megapascal (“MPa”); and peak load was recorded inunits of pound force (“lbf”), which was also converted to Newtons (“N”).Results were as listed in Table 24.

TABLE 24 Peak stress, psi Sample (MPa) Peak load, lbf (N) CE-3 1159.3(7.99) 579.6 (2578) EX-9 1057.9 (7.29) 528.9 (2353)

The samples which utilized the irradiated copper cage complex exhibitedadhesion that was essentially equivalent to the control samplesutilizing the copper (II) acetate, demonstrating the viability of thephoto-triggered redox cure for adhesive material.

What is claimed is:
 1. A polymerizable composition comprising apolymerizable ethylenically unsaturated component, and a redoxinitiation system comprising: a) an oxidizing agent, b) a reducingagent, and c) a photolabile transition metal complex of the formula:

wherein R^(photo) is a photolabile group; M⁺ is a transition metal thatparticipates in a redox cycle; each X¹ and X² is independently selectedfrom —N—, —S—, and —O—; each X³ and X⁴ is independently selected fromthe group consisting of —NR¹—, and —S—; each R¹ is independentlyselected from the group consisting of: H, alkyl, cycloalkyl,heterocycloalkyl, arylalkyl, heteroarylalkyl, alkoxy, halo, formyl,hydroxyl, acyl, aryloxy, alkylthio, amino, alkylamino, arylalkylamino,disubstituted amino, acylamino, acyloxy, ester, amide, and carboxyalkyl;each adjacent pair of R¹ and R² optionally independently form aheterocycloalkyl or heteroaryl group with respective heteroatom X³ orX⁴; each of R², R³, R⁴, R⁵, R⁶, and R⁷ is independently selected fromthe group consisting of: H, alkyl, alkenyl, alkynyl, cycloalkyl,cycloalkylalkyl, cycloalkylalkenyl, cycloalkylalkynyl, heterocyclo,heterocycloalkyl, heterocycloalkenyl, heterocycloalkynyl, aryl,arylalkyl, arylalkenyl, arylalkynyl, heteroaryl, heteroarylalkyl,heteroarylalkenyl, heteroarylalkynyl, alkoxy, halo, mercapto, azido,cyano, formyl, carboxylic acid, carboxyalkyl, hydroxyl, nitro, acyl,aryloxy, alkylthio, amino, alkylamino, arylalkylamino, disubstitutedamino, acylamino, acyloxy, ester, amide, sulfoxyl, sulfonyl, sulfonate,sulfonic acid, sulfonamide, urea, alkoxylacylamino, and aminoacyloxy;with the proviso that R³ is absent when R¹ and R² form a heteroarylgroup with respective heteroatom X³—X⁴; R⁴ and R⁵ optionally togetherform oxo; or R⁶ and R⁷ optionally together form oxo; x is from 1 to 2;and y is from 1 to 3; or a salt thereof.
 2. The polymerizablecomposition of claim 1 wherein the transition metal complex is of theformula:

wherein R^(Photo) is a photolabile group; M⁺ is a transition metal thatparticipates in a redox cycle; each X¹ and X² is independently selectedfrom —N—, —S—, and —O—; each X³ and X⁴ is independently selected fromthe group consisting of —NR¹—, and —S—; each R¹ is independentlyselected from the group consisting of: H, alkyl, cycloalkyl,heterocycloalkyl, arylalkyl, heteroarylalkyl, alkoxy, halo, formyl,hydroxyl, acyl, aryloxy, alkylthio, amino, alkylamino, arylalkylamino,disubstituted amino, acylamino, acyloxy, ester, amide, and carboxyalkyl;each of R², R³, R⁴, R⁵, R⁶, and R⁷ is independently selected from thegroup consisting of: H, alkyl, alkenyl, alkynyl, cycloalkyl,cycloalkylalkyl, cycloalkylalkenyl, cycloalkylalkynyl, heterocyclo,heterocycloalkyl, heterocycloalkenyl, heterocycloalkynyl, aryl,arylalkyl, arylalkenyl, arylalkynyl, heteroaryl, heteroarylalkyl,heteroarylalkenyl, heteroarylalkynyl, alkoxy, halo, mercapto, azido,cyano, formyl, carboxylic acid, carboxyalkyl, hydroxyl, nitro, acyl,aryloxy, alkylthio, amino, alkylamino, arylalkylamino, disubstitutedamino, acylamino, acyloxy, ester, amide, sulfoxyl, sulfonyl, sulfonate,sulfonic acid, sulfonamide, urea, alkoxylacylamino, and aminoacyloxy; R⁴and R⁵ optionally together form oxo; or R⁶ and R⁷ optionally togetherform oxo; R⁸ and R⁹ are independently a hydrocarbyl group when takenwith X³ and X⁴ respectively for a heterocyclic group or a heteroaromaticgroup, with the proviso that R³ is absent when R¹ and R² form aheteroaryl group with respective heteroatom X³— or X⁴; x is from 1 to 2;and y is from 1 to 3; or a salt thereof.
 3. The polymerizablecomposition of claim 1 wherein the transition metal complex is of theformula:

where R^(Photo) is a photolabile group; M⁺ is a transition metal thatparticipates in a redox cycle; the bracketed carbonyl is optional, andwhen absent is defined for R⁴ and R⁵ supra; and R^(hetero) is selectedfrom pyridine, imidazole and thiophene rings.
 4. The polymerizablecomposition of claim 1 wherein M⁺ is selected from copper, iron, cobaltor platinum.
 5. The polymerizable composition of claim 2 wherein theR⁸—X³ and/or the R⁹—X⁴ moiety is a pyridine, pyrazine, pyrimidine,thiazole, thiophene, isoquinoline imidazole or pyrroline heteroaromaticgroup.
 6. The polymerizable composition of claim 1, wherein thephotolabile group R^(Photo) is selected from phenacyl groups,2-alkylphenacyl groups, ethylene-bridged phenacyl groups,p-hydroxyphenacyl groups, benzoin groups, o-nitrobenzyl groups,o-nitro-2-phenethyloxycarbonyl groups, coumarin-4-yl methyl groups,benzyl groups, o-hydroxylbenzyl groups, o-hydroxynapthyl groups,2,5-dihydroxyl benzyl groups, 9-phenylthioxanthyl, 9-phenylxanthylgroups, anthraquinon-2-yl groups, 8-halo-7-hydroxyquinoline2-yl methylgroups, or pivaloylglycol groups.
 7. The polymerizable composition ofclaim 1 wherein the redox initiator system is present in the compositionin amounts, from 0.1 to about 10 parts by weight, based on 100 parts byweight of the polymerizable component of the polymerizable composition.8. The polymerizable composition of claim 1 wherein the polymerizableethylenically unsaturated component comprises: i. 85 to 100 parts byweight of an (meth)acrylic acid ester; ii. 0 to 15 parts by weight of anacid functional ethylenically unsaturated monomer; iii. 0 to 10 parts byweight of a non-acid functional, ethylenically unsaturated polarmonomer; iv. 0 to 5 parts vinyl monomer; and v. 0 to 5 parts of amultifunctional (meth)acrylate; vi. 0.1 to 10 parts by weight of theredox initiator system, based on 100 parts by weight of i) to v).
 9. Thepolymerizable composition of claim 8 further comprising 0.01 to 5 partsof a multifunctional (meth)acrylate.
 10. The polymerizable compositionof claim 1 comprising one or more polymerizable vinyl monomers and theredox initiator system.
 11. The polymerizable composition of claim 10wherein the vinyl monomer is selected from vinyl ethers, vinyl esters,styrenes, substituted styrene, vinyl halides, divinylbenzene, alkenes,isoprene, butadiene and mixtures thereof.
 12. The polymerizablecomposition of claim 1 wherein the molar ratio of photolabile transitionmetal complex relative to oxidizing agent is from 1:1000 to 1:5.
 13. Thepolymerizable composition of claim 1 wherein the mole ratio of theoxidant to reductant is from 1:1.5 to 1.5:1.
 14. The polymerizablecomposition of claim 1 wherein the oxidizing agent and reducing agentare present in an amount of 0.01% by weight to 10% by weight, based onthe total weight of the polymerizable component of the polymerizablecomposition.
 15. The polymerizable composition of claim 1 wherein thepolymerizable component comprises: i. up to 100 parts by weight of an(meth)acrylic acid ester; ii. 0 to 15 parts by weight of an acidfunctional ethylenically unsaturated monomer; iii. 0 to 15 parts byweight of a non-acid functional, ethylenically unsaturated polarmonomer; iv. 0 to 5 parts vinyl monomer; v. 0 to 100 parts of amultifunctional (meth)acrylate, relative to 100 parts i-iv; and vii. theredox initiator system in amounts from about 0.1 weight percent to about5.0 weight percent, relative to 100 parts total monomer i-v.
 16. Thepolymerizable composition of claim 15 comprising greater than 50 partsby weight of a multifunctional (meth)acrylate, based on the 100 parts byweight of i.-iv.
 17. The polymerizable composition of claim 1 furthercomprising 1-35 parts by weight of a toughening agent, relative to 100parts by weight of the polymerizable component of the polymerizablecomposition.
 18. The polymerizable composition of claim 1 wherein thepolymerizable ethylenically unsaturated component comprises a reactiveoligomer having pendent polymerizable groups.
 19. The polymerizablecomposition of claim 18 wherein the reactive oligomer comprises: a)greater than 50 parts by weight of (meth)acrylate ester monomer units;b) 0.5 to 10 parts by weight of monomer units having a pendent,free-radically polymerizable functional groups, c) 0 to 20 parts byweight of other polar monomer units, wherein the sum of the monomerunits is 100 parts by weight.